Dissertations / Theses on the topic 'Corrosion resistant materials'
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1
Freeman, Richard. "Corrosion & wear resistant materials for ballscrew actuator components." Thesis, University of Wolverhampton, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307165.
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Conrad, Heidi Ann. "Electrochemically Deposited Metal Alloy-silicate Nanocomposite Corrosion Resistant Materials." Thesis, University of North Texas, 2013. https://digital.library.unt.edu/ark:/67531/metadc271794/.
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Zinc-nickel ?-phase silicate and copper-nickel silicate corrosion resistant coatings have been prepared via electrochemical methods to improve currently available corrosion resistant materials in the oil and gas industry. A layered silicate, montmorillonite, has been incorporated into the coatings for increased corrosion protection. For the zinc nickel silicate coatings, optimal plating conditions were determined to be a working pH range of 9.3 -9.5 with a borate based electrolyte solution, resulting in more uniform deposits and better corrosion protection of the basis metal as compared to acidic conditions. Quality, strongly adhering deposits were obtained quickly with strong, even overall coverage of the metal substrate. The corrosion current of the zinc-nickel-silicate coating is Icorr = 3.33E-6 for a borate based bath as compared to a zinc-nickel bath without silicate incorporation (Icorr = 3.52E-5). Step potential and direct potential methods were examined, showing a morphological advantage to step potential deposition. The effect of borate addition was examined in relation to zinc, nickel and zinc-nickel alloy deposition. Borate was found to affect the onset of hydrogen evolution and was examined for absorption onto the electrode surface. For copper-nickel silicate coatings, optimal conditions were determined to be a citrate based electrolytic bath, with pH = 6. The solutions were stable over time and strong adhering, compact particle deposits were obtained. The corrosion current of the copper-nickel-silicate coatings is Icorr = 3.86E-6 (copper-nickel coatings without silicate, Icorr = 1.78E-4). The large decrease in the corrosion current as the silicate is incorporated into the coating demonstrates the increase in corrosion resistance of the coatings with the incorporation of silicates.
3
Bakare, Mayowa Sunday. "The effects of microstructural modifications on corrosion resistance of metallic corrosion resistant materials Inconel 625 and FeCrMoCB." Thesis, University of Nottingham, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.546474.
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Battu, Laurent P. "Corrosion resistance of modified [beta]-Eucryptite /." This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-08142009-040239/.
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Battu, Laurent P. "Corrosion resistance of modified β-Eucryptite." Thesis, Virginia Tech, 1991. http://hdl.handle.net/10919/44206.
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The corrosion resistance of chemically modified β-eucryptite (Li0.41Mg0.035AlP0.52Si0.480₄) having low expansion anisotropy and a near zero coefficient of thennal expansion was evaluated. Samples were exposed to aqueous hydrochloride acid at temperatures up to 100°C and environments containing sodium sulfate up to l000°C. The corrosion resistance was characterized by dilatometry, scanning electron microscopy, X-ray diffraction, energy dispersive x-ray analysis, weight variations, and mechanical properties variations.
The results show that modified β-eucryptite is more severely corroded than
commercial lithium-alumina-silicate glass-ceramics when exposed to these environments. Aqueous HCI removes AIP04 from modified β-eucryptite leaving a very porous structure. Molten salt corrodes modified β-eucryptite by penetration of sodium and sulfur which form an alkali melt under the surface. The modulus of rupture and the Young's modulus are reduced by both types of corrosion.Master of Science
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Leavitt, Leah A. "Biodegradable packaging for corrosion inhibition via supercriticial fluid." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/6013.
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Thesis (Ph. D.)--University of Missouri-Columbia, 2007.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on December 28, 2007) Includes bibliographical references.
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Armani, Alessandro. "Development of corrosion resistant coatings using natural biopolymer and pollen." Thesis, KTH, Materialvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-277932.
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Corrosion is a mechanism that highly reduces the lifetime of metals in different environments, especially in water or moisture environment. The worldwide maintenance cost due to corrosion is estimated in billions of dollars per year, and actual solutions in terms of coating usually contains toxic or environmentally harmful species. With an always increasing restriction by environmental restraints and regulations, a sustainable solution is urgently needed. Chitosan, easily obtained from chitin, the second most abundant biopolymer on earth, can be the solution to many problems. Crustacean shell waste is one of the major sources of chitin. Its resource efficiency, biocompatibility, and versatile physicochemical properties for chelation and crosslinking make chitosan a promising candidate as matrix material for biobased anticorrosive application. The purpose of the Master Thesis is to combine the properties of chitosan with the high porosity of bee pollen as anticorrosive agent carrier to obtain a fully sustainable solution for anticorrosive protection. The objective of this very ambitious project is to produce a composite material with a triple action: anticorrosive protection of metal surfaces, self-healing property of the coating and anti- biofouling activity. Results show that a biopolymer composite in forms of suspension or coatings with all desired components could be achieve. Specifically, a biopolymer nanocomposite composed of chitosan matrix, embedded with pollen grains that were loaded with anticorrosion agent 2- mercatobenzothiazole (MBT) in advance, and with zinc oxide nanoparticles have been produced. The physicochemical characterization of the biopolymer composite and its coatings, as well as electrochemical impedance spectroscopy (EIS) measurements on stainless steel plate with such coatings, suggest that a uniform and compact coating is obtained. Despite its good hydrophobicity with maximum contact angle 134.32 ± 3.84° with top coating, the chitosan nanocomposite coating is still permeable to water, partially because of the relatively big size of pollen (ca. 20 μm) that introduces gaps and interferes integrity of the coating. Therefore, a full immersion corrosion resistance is not achieved. In conclusion, phase transfer of hydrophobic pollen into hydrophilic chitosan matrix, MBT loading in pollen, ZnO encapsulation in chitosan, as well as crosslinking of chitosan, were successfully carried out. A coating based on such biopolymer nanocomposite is prepared on stainless steel and investigated on its anti-corrosion property. Future work will be choosing a proper sized pollen as a microcontainer to enhance the integrity of the coating, and eventually endow the coating with the three-in-one function, i.e., anticorrosion, antimicrobial, and self-healing.Korrosion är en mekanism som kraftigt reducerar livslängden för metaller i olika miljöer, särskilt i vatten- eller fuktmiljö. De globala underhållskostnaderna på grund av korrosion uppskattas i miljarder dollar per år, och faktiska lösningar med avseende på beläggning innehåller vanligtvis giftiga eller miljöfarliga arter. Med en ständigt ökande begränsning genom miljörestriktioner och bestämmelser krävs det en hållbar lösning. Kitosan, den näst vanligaste biopolymeren, kan vara lösningen på många problem. Skaldjuravfall är en av de viktigaste källorna till kitosan. Dess resurseffektivitet, biokompatibilitet och mångsidiga fysikalisk-kemiska egenskaper för kelering och tvärbindning gör kitosan till en lovande kandidat som matrismaterial för biobaserade antikorrosiva applikationer. Syftet med denna masteruppsats är att kombinera egenskaperna hos kitosan med den höga porositeten hos bipollen som antikorrosivt medel för att erhålla en helt hållbar lösning för korrosionsskydd. Målet med detta mycket ambitiösa projekt är att producera ett sammansatt material med en tredubbel verkan: korrosionsskydd för metallytor, självhelande egenskap hos beläggningen och anti- biobeväxningsaktivitet. Resultaten visar att en biopolymerkomposit i form av suspension eller beläggningar med alla önskade komponenter kan uppnås. Specifikt har en biopolymer-nanokomposit sammansatt av kitosanmatris med inbäddade pollenkorn, som i förväg packats med antikorrosionsmedlet 2-mercaptobenzotiazol (MBT) och med zinkoxid-nanopartiklar, producerats. Den fysikalisk-kemiska karakteriseringen av biopolymerkompositen och dess beläggningar, liksom elektrokemiska impedansspektroskopimätningar (EIS) på rostfri stålplåt med sådana beläggningar tyder på att en enhetlig och kompakt beläggning erhålls. Trots sin goda hydrofobi med maximal kontaktvinkel 134,32 ± 3,84° med toppbeläggningen, är nanokompositbeläggningen av kitosan fortfarande permeabel för vatten, delvis på grund av den relativt stora storleken hos pollen (ca. 20 μm) som introducerar luckor och stör integriteten hos beläggningen. Därför uppnås inte en fullständig immersionskorrosionsbeständighet. Sammanfattningsvis genomfördes fasövergång av hydrofobt pollen till hydrofil kitosanmatris, MBT-packning i pollen, ZnO-inkapsling i kitosan, samt tvärbindning av kitosan med framgång. En beläggning baserad på sådan biopolymer-nanokomposit framställs på rostfritt stål och undersöks med avseende på dess korrosionsegenskaper. Framtida arbete kommer att bestå i att välja en lämplig storlek av pollen som en mikrobehållare för att förbättra beläggningens integritet, och så småningom förse beläggningen med tre-i-ett-funktionen, dvs.antikorrosion, antimikrobiell och självhelande.
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Cotterrell, M. H. "The influence of water composition on the pitting behaviour of newly developed corrosion resistant steels." Master's thesis, University of Cape Town, 1988. http://hdl.handle.net/11427/21134.
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Bibliography: pages 96-103.The mechanisation of the working stapes in South African gold mines has required the introduction of a fundamentally new technology, hydro-power, in which machines are powered hydraulically using mine water fed from above ground. Mine water is aggressive and has a variable acidity and pH, and contains high concentrations of sulphate, chloride and nitrate ions. In order to minimise the pitting corrosion of piping and stoping machinery a compromise between selecting a suitable corrosion resistant material and treating the mine water to an acceptable level of corrosiveness is being sought.
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Tan, Swee Hain. "Organic corrosion inhibitors." Thesis, Tan, Swee Hain (1991) Organic corrosion inhibitors. PhD thesis, Murdoch University, 1991. https://researchrepository.murdoch.edu.au/id/eprint/333/.
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The overall aims of this thesis were to conduct a broad survey of possible organic corrosion inhibitors in near-neutral chloride solutions and to elucidate the mechanisms of such action.
Altogether, 130 organic compounds were studied as possible corrosion inhibitors for pure iron, mild steel, copper and aluminium in aerated near-neutral (pH = 8.4) solutions containing 500 ppm NaCl and 100 ppm NaHCO, conditions often encountered in water-based automotive engine coolants. Inhibitor behaviour was investigated using steady-state electrochemical techniques including polarisation curves, Stern-Geary and corrosion potential (Em,) measurements. The organic compounds examined were found to be highly specific in their inhibitive action toward the metals studied. Typical examples of highly effective corrosion inhibitors were: sebacate and octanoate for pure iron; oleate and sebacate for mild steel; benzotriazole and 2-mercaptobenzothiazole for copper; and laurate and oleate for aluminium. E, was found to provide a rapid and convenient screening test for evaluating the inhibitor performance of organic compounds toward pure iron, mild steel and aluminium but was less useful for copper.
Good organic inhibitors were found to act as anodic inhibitors toward pure iron and mild steel but as anodic or mixed-type inhibitors toward copper. For aluminium, the majority of the compounds studied were found to act as anodic inhibitors. However,However, it was also found that only pit initiation was inhibited, i.e. existing pits were not prevented from developing. Optical microscopy of pitted aluminium surfaces indicated their nature varied considerably with inhibition efficiency. The role of complex formation in organic corrosion inhibitors was found to vary with the metal. Complexation of either iron(I1) or iron(II1) ions was found to have an insignificant effect on mild steel. The corrosion rate of copper was found to increase with the copper(LI) complex stability, thus indicating complex formation to be the rate-determining step. For aluminium, the observed effects were found to depend on complex stability. For weak to moderate complexants, inhibitor efficiency (measured as E,,) increased with increasing complexation. However, very strong complexing agents were sufficiently stable to dissolve the aluminium oxide surface, leading to poor inhibition. Aluminium pit morphology was found, using scanning electron microscopy, to change from hemispherical in the uninhibited solution to irregular in the presence of complexing inhibitors. No simple relationships between inhibitor efficiency and molecular structure were found. However, carbon chain length, the nature of functional group(s) and their location in the molecule were found to be important but varied according to the metal.
The inhibiting ability of sebacate (a straight chain C, dicarboxylate) was found not to be compromised by water movement (stirring) or pre-existing corrosion product layers. Immersion tests showed that passive film formation on mild steel in sebacate solution involved two stages and was complete only after -100 h immersion.
The ion selective properties of several iron(II1) carboxylates and hydrated iron(II1) oxide films were studied by membrane potential measurements in neutral sodium chloride solutions. Some specimens were also studied by Mossbauer spectroscopy. These results show that dicarboxylates are good inhibitors toward mild steel because they form impermeable films. Poor inhibitor performance is associated with the anion selectivity of the film which in turn appears to be related to the film purity. A model is suggested for the inhibition mechanism of mild steel corrosion by dicarboxylates in aerated near-neutral chloride solutions.
10
Tan, Swee Hain. "Organic corrosion inhibitors." Murdoch University, 1991. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20060818.150145.
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The overall aims of this thesis were to conduct a broad survey of possible organic
corrosion inhibitors in near-neutral chloride solutions and to elucidate the
mechanisms of such action.
Altogether, 130 organic compounds were studied as possible corrosion inhibitors for
pure iron, mild steel, copper and aluminium in aerated near-neutral (pH = 8.4)
solutions containing 500 ppm NaCl and 100 ppm NaHCO,, conditions often
encountered in water-based automotive engine coolants. Inhibitor behaviour was
investigated using steady-state electrochemical techniques including polarisation
curves, Stern-Geary and corrosion potential (Em,) measurements.
The organic compounds examined were found to be highly specific in their
inhibitive action toward the metals studied. Typical examples of highly effective
corrosion inhibitors were: sebacate and octanoate for pure iron; oleate and sebacate
for mild steel; benzotriazole and 2-mercaptobenzothiazole for copper; and laurate
and oleate for aluminium.
E, was found to provide a rapid and convenient screening test for evaluating the
inhibitor performance of organic compounds toward pure iron, mild steel and
aluminium but was less useful for copper.
Good organic inhibitors were found to act as anodic inhibitors toward pure iron and
mild steel but as anodic or mixed-type inhibitors toward copper. For aluminium,
the majority of the compounds studied were found to act as anodic inhibitors.
However,However, it was also found that only pit initiation was inhibited, i.e. existing pits
were not prevented from developing. Optical microscopy of pitted aluminium
surfaces indicated their nature varied considerably with inhibition efficiency.
The role of complex formation in organic corrosion inhibitors was found to vary
with the metal. Complexation of either iron(I1) or iron(II1) ions was found to have
an insignificant effect on mild steel. The corrosion rate of copper was found to
increase with the copper(LI) complex stability, thus indicating complex formation to
be the rate-determining step. For aluminium, the observed effects were found to
depend on complex stability. For weak to moderate complexants, inhibitor
efficiency (measured as E,,) increased with increasing complexation. However, very
strong complexing agents were sufficiently stable to dissolve the aluminium oxide
surface, leading to poor inhibition. Aluminium pit morphology was found, using
scanning electron microscopy, to change from hemispherical in the uninhibited
solution to irregular in the presence of complexing inhibitors.
No simple relationships between inhibitor efficiency and molecular structure were
found. However, carbon chain length, the nature of functional group(s) and their
location in the molecule were found to be important but varied according to the
metal.
The inhibiting ability of sebacate (a straight chain C, dicarboxylate) was found not
to be compromised by water movement (stirring) or pre-existing corrosion product
layers. Immersion tests showed that passive film formation on mild steel in
sebacate solution involved two stages and was complete only after -100 h
immersion.
The ion selective properties of several iron(II1) carboxylates and hydrated iron(II1)
oxide films were studied by membrane potential measurements in neutral sodium
chloride solutions. Some specimens were also studied by Mossbauer spectroscopy.
These results show that dicarboxylates are good inhibitors toward mild steel because
they form impermeable films. Poor inhibitor performance is associated with the
anion selectivity of the film which in turn appears to be related to the film purity.
A model is suggested for the inhibition mechanism of mild steel corrosion by
dicarboxylates in aerated near-neutral chloride solutions.
11
Agaponova, Anna Vladimirovna. "ENCAPSULATION METHOD FOR SURFACE ENGINEERING OF CORROSION-RESISTANT ALLOYS BY LOW-TEMPERATURE NITRO-CARBURIZATION." Case Western Reserve University School of Graduate Studies / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1439576651.
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Moser, Robert David. "High-strength stainless steels for corrosion mitigation in prestressed concrete: development and evaluation." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41083.
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The use of stainless steel alloys in reinforced concrete structures has shown great success in mitigating corrosion in even the most severe of exposures. However, the use of high-strength stainless steels (HSSSs) for corrosion mitigation in prestressed concrete (PSC) structures has received limited attention. To address these deficiencies in knowledge, an experimental study was conducted to investigate the feasibility of using HSSSs for corrosion mitigation in PSC. The study examined mechanical behavior, corrosion resistance, and techniques for the production of HSSS prestressing strands. Stainless steel grades 304, 316, 2101, 2205, 2304, and 17-7 along with a 1080 prestressing steel control were included in the study. Tensile strengths of 1250 to 1550 MPa (181 to 225 ksi) were achieved in the cold-drawn HSSSs. 1000 hr stress relaxation of all candidate HSSSs was predicted to be between 6 and 8 % based on the results of 200 hr tests conducted at 70 % of the ultimate tensile strength. Residual stresses due to the cold drawing had a significant influence on stress vs. strain behavior and stress relaxation. Electrochemical corrosion testing found that in solutions simulating alkaline concrete, all HSSSs showed exceptional corrosion resistance at chloride (Cl-) concentrations from zero to 0.25 M. However, when exposed to solutions simulating carbonated concrete, corrosion resistance was reduced and the only HSSSs with acceptable corrosion resistance were duplex grades 2205 and 2304, with 2205 resistant to corrosion initiation at Cl- concentrations up to 1.0 M (twice that in seawater). Based on these results, duplex grades 2205 and 2304 were identified as optimal HSSSs and were included in additional studies which found that: (1) 2304 is susceptible to corrosion when tested in a stranded geometry, (2) 2205 and 2304 are not susceptible to stress corrosion cracking, and (3) 2205 and 2304 are susceptible to hydrogen embrittlement. Efforts focused on the production of 2205 and 2304 prestressing strands showed that they could be produced as strands using existing ASTM A416 prestressing strand production facilities. Due to the ferromagnetic properties of 2205 and 2304, a low-relaxation heat treatment was found to be a viable option to reduce stress relaxation and improve mechanical properties. The overall conclusion of the study was that HSSSs, especially duplex grades 2205 and 2304, show excellent promise to mitigate corrosion if utilized as prestressing reinforcement in PSC structures exposed to severe marine environments.
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Mohanta, Paritosh Kumar [Verfasser]. "Corrosion resistant cathode catalyst support materials for polymer electrolyte membrane fuel cell / Paritosh Kumar Mohanta." Ulm : Universität Ulm, 2017. http://d-nb.info/1137946474/34.
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Alexis, naza. "Corrosion behavior of lead-free and dezincification resistant brass alloys in tap water." Thesis, KTH, Kemi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-299738.
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Avzinkningshärdiga och blyfria mässingslegeringar används i stor utsträckning för att ersätta blyinnehållande mässingslegeringar som används för dricksvattensapplikationer. På grund av det begränsade antalet korrosionsstudier av dessa legeringar är syftet med denna studie att belysa hur vattensammansättning, temperatur och exponeringstid kan påverka legeringarnas korrosionsegenskaper. Tre avzinkningshärdiga mässingslegeringar studerades i kranvatten; två blyfria mässingslegeringar (CW511L och CW724R) och en blyinnehållande mässingslegering (CW602N) som betraktades som ett referensmaterial. En kombination av elektrokemiska, mikroskopiska och ytanalystekniker användes för att utforska korrosionstyp, mekanismer samt korrosionshastighet. Även om samtliga legeringar visade godkända egenskaper i avzinkningstestet enligt ISO 6509-1:2014 var målet att bedöma deras korrosionsbeteende i kranvatten. Vattenkemin justerades för att undersöka effekten av pH, kloridkoncentration och alkalinitet hos de tre mässingslegeringarna under kortvarig exponeringstid (24 timmar). Vattnets korrosivitet varierade beroende på mässingslegeringens sammansättning. Det visade sig att CW511L var känsligare för höga kloridkoncentrationer (44.7 mg/L) och hög alkalinitet (310 mg/L) än för lågt pH (6.9). Det motsatta observerades dock för både CW724R och CW602N. Testvattnets aggressivitet påverkades också av temperaturen när den ökades från 22 °C till 50 °C under exponering i 24 timmar. Medan ingen tydlig avzinkning upptäcktes observerades en kombination av både allmän och lokal korrosion i varierande utsträckning mellan de olika legeringarna. Initieringen av det lokala korrosionsangreppet varierade både med testvattnets kemi och med legeringssammansättningen. Medan CW724R och CW602N bägge uppvisade hög känslighet för lokal korrosion i vattnet med högst pH (8.2), var CW511L mer känslig i det vatten med lågt pH (6.9) vid 50 °C. Effekten av exponeringstid undersöktes i vattnet med högst pH (8.2) för de tre mässingslegeringarna upp till 72 dagar. Korrosionshastigheten baserad på viktminskning visade en förväntad hög korrosionshastighet som minskade med kontinuerlig exponeringstid, vilket ledde till en låg korrosionshastighet för alla tre mässingslegeringarna efter 72 dagar. De blyfria mässingslegeringar uppvisade ur detta perspektiv goda korrosionsegenskaper som är konkurrenskraftiga med mässing som innehåller bly.Dezincification resistant (DZR) and lead-free brass alloys continue to be widely applied replacing lead containing brasses in the drinking water sector. Due to the limited number of corrosion studies of these alloys in tap water, the present thesis was initiated with the aim to understand how the water type, its temperature and exposure duration can affect the corrosion behavior. Three DZR brass alloys were studied in order to evaluate their corrosion behavior in tap water of varying characteristics. The alloys included were two lead-free brasses (CW511L and CW724R) and a leaded brass alloy (CW602N) considered as a reference material. A combination of electrochemical, microscopic and surface analytical techniques were adopted to explore the corrosion form, mechanisms and corrosion rate. While these alloys passed the dezincification test as per ISO 6509-1:2014, the aim was to assess their corrosion performance in tap water. The influence of water chemistry parameters including pH, chloride concentration and alkalinity on the corrosion resistance of the three DZR alloys was investigated in short-term exposures (24 h). Depending on the brass alloy, the corrosivity of the test waters varied. The results show grade CW511L to be more sensitive in tap water of higher chloride concentration (44.7 mg/L) and alkalinity (310 mg/L) compared with low pH (6.9). However, opposite results were obtained for both CW724R and CW602N. The corrosivity of the test water was also affected by the temperature when increased from 22°C to 50°C during 24 h of immersion. While no dezincification features were observed on the surfaces, a combination of general and localized corrosion was observed to a largely variable extent between the alloys. The extent of initiation of localized corrosion varied with test water and alloy composition. While CW724R and CW602N showed similar high susceptibility to localized corrosion in the alkaline (pH 8.2) tap water, CW511L was more prone to pitting corrosion in tap water of low pH (6.9). The effect of exposure duration was explored in the alkaline test water for the three brasses up to 72 days. Corrosion rates based on weight loss showed an expected initial high corrosion rate which declined with continuous immersion, leading to low and similar corrosion rates for all three brass alloys after 72 days. Thus, at given test conditions, the lead-free brasses showed good corrosion behavior being competitive to the performance of lead containing brass. Therefore, lead-free brass alloys are good candidates to substitute lead-containing brasses in tap water applications.
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Tientong, Jeerapan. "Electrodeposition of Nickel and Nickel Alloy Coatings with Layered Silicates for Enhanced Corrosion Resistance and Mechanical Properties." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc699999/.
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The new nickel/layered silicate nanocomposites were electrodeposited from different pHs to study the influence on the metal ions/layered silicate plating solution and on the properties of the deposited films. Nickel/layered silicate nanocomposites were fabricated from citrate bath atacidic pHs (1.6−3.0), from Watts’ type solution (pH ~4-5), and from citrate bath at basic pH (~9). Additionally, the new nickel/molybdenum/layered silicate nanocomposites were electrodeposited from citrate bath at pH 9.5. The silicate, montmorillonite (MMT), was exfoliated by stirring in aqueous solution over 24 hours. The plating solutions were analyzed for zeta potential, particle size, viscosity, and conductivity to investigate the effects of the composition at various pHs. The preferred crystalline orientation and the crystalline size of nickel, nickel/layered silicate, nickel/molybdenum, and nickel/molybdenum/layered silicate films were examined by X-ray diffraction. The microstructure of the coatings and the surface roughness was investigated by scanning electron microscopy and atomic force microscopy. Nickel/molybdenum/layered silicate nanocomposites containing low content of layered silicate (1.0 g/L) had increase 32 % hardness and 22 % Young’s modulus values over the pure nickel/molybdenum alloy films. The potentiodynamic polarization and electrochemical impedance measurements showed that the nickel/molybdenum/layered silicate nanocomposite layers have higher corrosion resistance in 3.5% NaCl compared to the pure alloy films. The corrosion current density of the nickel/molybdenum/layered silicate nanocomposite composed of 0.5 g/L MMT is 0.63 µA·cm-2 as compare to a nickel/molybdenum alloy which is 2.00 µA·cm-2.
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Rajamani, Deepika. "Processing and Properties of Environmentally-Friendly Corrosion Resistant Hybrid Nanocomposite Coatings for Aluminum Alloy AA2024." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1138811300.
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Raseroka, Mantsaye S. "Controlled chloride cracking of austenitic stainless steel." Pretoria : [s.n.], 2009. http://upetd.up.ac.za/thesis/available/etd-07032009-120615/.
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Shreeram, Devesh Dadhich. "Development of Wear and Corrosion Resistant Nickel Based Coatings Through Pulse Reverse Current (PRC) Electrodeposition Process." University of Akron / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=akron1509839587682532.
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Rizvi, Hussain R. "Bioinspired & biocompatible coatings of poly(butylene adipate-co-terephthalate) and layer double hydroxide composites for corrosion resistance." Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc849647/.
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Hierarchical arrangement of biological composites such as nacre and bone containing high filler (ceramic) content results in high strength and toughness of the natural material. In this study we mimic the design of layered bone microstructure and fabricate an optimal multifunctional bio-nanocomposite having strength, toughness and corrosion resistance. Poly (butylene adipate-co-terephthalate) (PBAT), a biodegradable polymer was used as a substrate material with the reinforcement of LDH (Layered double hydroxide) as a nanofiller in different concentrations to achieve enhancement in mechanical properties as well as processing related thermostability. Corrosion resistance was increased by mimicking a layered structured which incorporated a tortuous diffusion path.
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Johnson, Stephanie Lee. "Surface studies of potentially corrosion resistant thin film coatings on chromium and type 316L stainless steel." Diss., Manhattan, Kan. : Kansas State University, 2006. http://hdl.handle.net/2097/236.
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Kang, Min. "Alkali/steam corrosion resistance of commercial SiC products coated with sol-gel deposited Mg-doped Al₂TiO₅ and CMZP." Thesis, Virginia Tech, 1994. http://hdl.handle.net/10919/42006.
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The corrosion resistance of two commercially available SiC filter materials coated with Mg-doped
Al2 Ti05 and (Ca 0.6.6' Mg0.52)
Zr4P6024 (CMZP) was investigated in high-temperature high pressure
(HTHP) alkali-steam environments. Coated specimen properties, including cold and hot
compressive strengths, bulk density, apparent porosity, permeability, and weight change,
dete~ed after exposure to 92% air-S% steam 10 ppm Na at 8OO°C and 1.8 MPs for 500 h were
compared with those of uncoated specimens. Procedures for applying homogeneous coatings of
Mg-doped Al2 Ti05 and CMZP to porous SiC filters were established and coating of the materials
was successfully accomplished. Efforts to stabilize the Al2 Ti05 coating composition at elevated
temperature were successful. Coatings show promise for providing improved corrosion resistance
of the materials in pressurized fluidized bed combustion (PFBC) environments as evidenced by
higher compressive strengths exhibited by coated SiC specimens than by uncoated SiC specimens
following HTHP alkali-steam exposure.
Master of Science
22
Xu, Danhua. "A Study of magnetic thin film corrosion mechanisms with the development of a novel on-line coupling technique and with Microstructural and Magnetic Cross-Sectional Profiling Techniques." Full text open access at:, 2008. http://content.ohsu.edu/u?/etd,648.
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Mohan, Prabhakar. "Environmental Degradation of Oxidation Resistant and Thermal Barrier Coatings for Fuel-Flexible Gas Turbine Applications." Doctoral diss., University of Central Florida, 2010. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3013.
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The development of thermal barrier coatings (TBCs) has been undoubtedly the most critical advancement in materials technology for modern gas turbine engines. TBCs are widely used in gas turbine engines for both power-generation and propulsion applications. Metallic oxidation-resistant coatings (ORCs) are also widely employed as a stand-alone protective coating or bond coat for TBCs in many high-temperature applications. Among the widely studied durability issues in these high-temperature protective coatings, one critical challenge that received greater attention in recent years is their resistance to high-temperature degradation due to corrosive deposits arising from fuel impurities and CMAS (calcium-magnesium-alumino-silicate) sand deposits from air ingestion. The presence of vanadium, sulfur, phosphorus, sodium and calcium impurities in alternative fuels warrants a clear understanding of high-temperature materials degradation for the development of fuel-flexible gas turbine engines. Degradation due to CMAS is a critical problem for gas turbine components operating in a dust-laden environment. In this study, high-temperature degradation due to aggressive deposits such as V2O5, P2O5, Na2SO4, NaVO3, CaSO4 and a laboratory-synthesized CMAS sand for free-standing air plasma sprayed (APS) yttria stabilized zirconia (YSZ), the topcoat of the TBC system, and APS CoNiCrAlY, the bond coat of the TBC system or a stand-alone ORC, is examined. Phase transformations and microstructural development were examined by using x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. This study demonstrated that the V2O5 melt degrades the APS YSZ through the formation of ZrV2O7 and YVO4 at temperatures below 747°C and above 747°C, respectively. Formation of YVO4 leads to the depletion of the Y2O3 stabilizer and the deleterious transformation of the YSZ to the monoclinic ZrO2 phase. The investigation on the YSZ degradation by Na2SO4 and a Na2SO4 + V2O5 mixture (50-50 mol. %) demonstrated that Na2SO4 itself did not degrade the YSZ, however, in the presence of V2O5, Na2SO4 formed vanadates such as NaVO3 that degraded the YSZ through YVO4 formation at temperature as low as 700°C. The APS YSZ was found to react with the P2O5 melt by forming ZrP2O7 at all temperatures. This interaction led to the depletion of ZrO2 in the YSZ (i.e., enrichment of Y2O3 in t' -YSZ) and promoted the formation of the fluorite-cubic ZrO2 phase. Above 1250°C, CMAS deposits were observed to readily infiltrate and significantly dissolve the YSZ coating via thermochemical interactions. Upon cooling, zirconia reprecipitated with a spherical morphology and a composition that depended on the local melt chemistry. The molten CMAS attack destabilized the YSZ through the detrimental phase transformation (t -> t -> f + m). Free standing APS CoNiCrAlY was also prone to degradation by corrosive molten deposits. The V2O5 melt degraded the APS CoNiCrAlY through various reactions involving acidic dissolution of the protective oxide scale, which yielded substitutional-solid solution vanadates such as (Co,Ni)3(VO4)2 and (Cr,Al)VO4. The molten P2O5, on the other hand, was found to consume the bond coat constituents significantly via reactions that formed both Ni/Co rich phosphates and Cr/Al rich phosphates. Sulfate deposits such as Na2SO4, when tested in encapsulation, damaged the CoNiCrAlY by Type I acidic fluxing hot corrosion mechanisms at 1000°C that resulted in accelerated oxidation and sulfidation. The formation of a protective continuous Al2O3 oxide scale by preoxidation treatment significantly delayed the hot corrosion of CoNiCrAlY by sulfates. However, CoNiCrAlY in both as-sprayed and preoxidized condition suffered a significant damage by CaSO4 deposits via a basic fluxing mechanism that yielded CaCrO4 and CaAl2O4. The CMAS melt also dissolved the protective Al2O3 oxide scale developed on CoNiCrAlY by forming anorthite platelets and spinel oxides. Based on the detailed investigation on degradation of the APS YSZ and CoNiCrAlY by various corrosive deposits, an experimental attempt was carried out to mitigate the melt-induced deposit attack. Experimental results from this study demonstrate, for the first time, that an oxide overlay produced by electrophoretic deposition (EPD) can effectively perform as an environmental barrier overlay for APS TBCs. The EPD protective overlay has a uniform and easily-controllable thickness, uniformly distributed closed pores and tailored chemistry. The EPD Al2O3 and MgO overlays were successful in protecting the APS YSZ TBCs against CMAS attack and hot corrosion attack (e.g., sulfate and vanadate), respectively. Furnace thermal cyclic oxidation testing of overlay-modified TBCs on bond-coated superalloy also demonstrated the good adhesive durability of the EPD Al2O3 overlay.Ph.D.
Department of Mechanical, Materials and Aerospace Engineering
Engineering and Computer Science
Materials Science & Engr PhD
24
LEITE, ANTONIO M. dos S. "Investigação da resistência à corrosão por pites do aço inoxidável duplex tipo 2404 (UNS S82441) submetido à soldagem por atrito com pino não-consumível (FSW)." reponame:Repositório Institucional do IPEN, 2017. http://repositorio.ipen.br:8080/xmlui/handle/123456789/28016.
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Submitted by Pedro Silva Filho (pfsilva@ipen.br) on 2017-11-17T16:32:32Z
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Os aços inoxidáveis duplex são largamente utilizados na fabricação de equipamentos para a indústria de óleo e gás, utilizados tanto no ambiente onshore quanto offshore. Sua grande limitação é que, com o aumento de temperatura, ocorre precipitação de fases indesejáveis, que reduzem drasticamente a resistência à corrosão e as propriedades mecânicas desses materiais. Considerando o efeito deletério da soldagem a fusão nos aços inoxidáveis duplex, a soldagem por atrito com pino não-consumível (FSW) é amplamente considerada como alternativa aos processos convencionais. Como no FSW a união dos materiais ocorre no estado sólido, muitos dos problemas de soldabilidade associados às técnicas tradicionais de soldagem por fusão são evitados. Neste trabalho, amostras retiradas da zona misturada (ZM), das zonas afetadas pelo calor (ZTA e ZTMA) e do metal de base (MB) de chapas de aço inoxidável lean duplex LDX 2404® (UNS S82441) soldadas por atrito com pino não-consumível foram caracterizadas microestruturalmente e tiveram sua resistência à corrosão avaliada por meio de ensaios eletroquímicos. Os resultados obtidos nos ensaios eletroquímicos indicaram que as zonas afetadas pelo calor e a ZM se mantiveram tão resistentes à corrosão localizada quanto o MB. Permitiram concluir também que a excelente resistência à corrosão da liga está associada ao teor elevado de N.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
25
Behrani, Vikas. "Surface Modifications of Steels to Improve Corrosion Resistance in Sulfidizing-Oxidizing Environments." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19708.
Full textAbstract:
Industrial and power generation processes employ units like boilers and gasifiers to burn sulfur containing fuels to produce steam and syn gas (H2 and CO), which can generate electricity using turbines and fuel cells. These units often operate under environments containing gases such as H2S, SO2, O2 etc, which can attack the metallic structure and impose serious problems of corrosion. Corrosion control in high temperature sulfur bearing environments is a challenging problem requiring information on local gaseous species at the surface of alloy and mechanisms of degradation in these environments. Coatings have proved to be a better alternative for improving corrosion resistance without compromising the bulk mechanical properties. Changes in process conditions may result in thermal and/or environment cycling between oxidizing and sulfidizing environments at the alloy surface, which can damage the protective scale formed on the alloy surface, leading to increase in corrosion rates. Objective of this study was to understand the effect of fluctuating environments on corrosion kinetics of carbon steels and develop diffusion based coatings to mitigate the high temperatures corrosion under these conditions. More specifically, the focus was : (1) to characterize the local gaseous environments at the surface of alloys in boilers; (2) optimizing diffusion coatings parameters for carbon steel; (3)understand the underlying failure mechanisms in cyclic environments; (4) to improve aluminide coating behavior by co-deposition of reactive elements such as Yttrium and Hafnium; (5) to formulate a plausible mechanism of coating growth and effects of alloying elements on corrosion; and (6) to understand the spallation behavior of scale by measuring stresses in the scales. The understanding of coating mechanism and effects of fluctuating gaseous environments provides information for designing materials with more reliable performance. The study also investigates the mechanism behind the effect of REs on scale adhesion and sulfidation behavior. Thus, the present work will have a broad impact on the field of materials and coatings selection for high temperature industrial environments such as boilers and gasifiers, and provides information on RE-modified aluminized coatings on carbon steel as an alternative for the use of bulk superalloys under high temperature sulfur bearing environments.
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Strahin, Brandon L. "WEAR AND CORROSION RESISTANT TRIBOLOGICAL SURFACE TREATMENTS FOR TITANIUM ALLOYS: EVALUATION OF COMPLIMENTARY AND SUPPLEMENTARY DUPLEX TREATMENT PROCESSES." University of Akron / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=akron1555110923128525.
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Nilsson, Erik A. A. "Degradation Mechanisms of Heat Resistant Steel at Elevated Temperatures : In an Iron Ore Pelletizing Industry." Doctoral thesis, Luleå tekniska universitet, Materialvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-62162.
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This thesis focuses on the different degradation mechanisms of the stainless steel in a travelling grate in a Grate-Kiln iron ore pellet indurator. The travelling grate is a conveyor belt that transports green-body pellets to a rotary kiln while the pellets are being dried and pre-heated to a temperature of 900-1100 °C by recycled hot air. After unloading of the pellets to the rotary-kiln for further sintering, the travelling grate is cooled in room temperature while returning to the loading zone of the wet pellets. The steel was tested during thermal cycling in a test-rig, in order to simulate the influence of thermo mechanical fatigue and oxide spallation. The influence of erosion-deposition was investigated in a modified horizontal industrial combustion kiln at 800 °C, with slag and coal from production used as erosive media and combustion fuel, respectively. The influence of minor alloying additions of Mn, Si and Ti on the microstructure was explored by eight different casted alloy compositions. Isothermal heat treatments were performed at 800 °C during 200 hours on steel immersed in deposits recovered from a travelling grate in production. The three main degradation mechanisms found in this work are thermal spallation, erosion-deposition and deposit induced accelerated corrosion (DIAC). Thermal spallation of the oxide layer is caused by the thermal expansion difference between the oxide and the metal during heating and cooling. It has been found that Ti improves the spallation resistance while Si reduces it. Spallation of deposits is another cause believed to increase the degradation. Erosion-deposition appears due to simultaneous erosion and deposition of particles on the travelling grate that causes erosion or deposition depending on the amount of alkali metals in the environment. The velocity of the particles also influences erosion and deposition in the way that higher velocities increase erosion. DIAC is proposed to form on the travelling grate due to the concentration of chloride- and sulphate containing alkali metals in the deposits. Other than these major degrading mechanisms, minor degradation mechanisms such as internal oxidation, sigma formation, carburization and sensitization towards inter-granular attack have been found inside the steel during heating. Thermo mechanical fatigue (TMF) causes intergranular cracks in the material of the travelling grate. Casting issues such as micro-segregation have also been addressed in this thesis. A few different ways to improve degradation resistance have been proposed, such as homogenization heat treatments, optimization of process parameters and inhibitor solutions.
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Díaz, Jorge G. "Effect of Amines as Corrosion Inhibitors for a Low Carbon Steel in Power Industry." Thesis, University of North Texas, 2004. https://digital.library.unt.edu/ark:/67531/metadc4666/.
Full textAbstract:
Commonly used amines in power industry, including morpholine, DBU (1,8-diazabicyclo[5.4.0]undec-7-ene), and DMA (dimethylallylamine) were evaluated for their effect on AISI 1018 steel at 250oF. Samples were exposed to an autoclave containing amine added aqueous solution at pH of 9.5 for 1, 2, 4, 6, 8, and 12 hours. Morphology studies were carried using scanning electron microscope (SEM), phase analysis was done utilizing Fourier transform infrared spectroscopy (FTIR), and weight loss was performed to assess kinetics of oxidation. Control samples showed the highest metal dissolution rate. DBU showed the best performance in metal protection and SEM indicated the presence of a free-crack layer formed by fine particles in that set. FTIR showed that DBU apparently favored the formation of magnetite. It is believed that fine particles impede intrusion of aggressive ions into the metal surface by forming a barrier layer. FTIR demonstrated that DMA formed more oxyhydroxides, whereas morpholine presented magnetite to hematite transformation as early as 2 hours. SEM revealed that control and DMA produced acicular particles characteristic of oxyhydroxides while morpholine and DBU presented more equiaxed particles.
29
Lin, Hsin-Yi. "Short term observations of in vitro biocorrosion of two commonly used implant alloys." Diss., Mississippi State : Mississippi State University, 2002. http://library.msstate.edu/etd/show.asp?etd=etd-08202002-105908.
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Peixoto, Leandro César de Lorena. "Microestrutura de solidificação e resistencias mecanicas e a corrosão de ligas Pb-Sn diluidas." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/264545.
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Orientadores: Amauri Garcia, Wislei Riuper OsorioDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: Produtores de baterias chumbo-ácido têm modificado os processos de produção e composição química das ligas utilizadas nas grades das baterias com intuito de diminuir o seu peso final, bem como reduzir os custos de produção e também aumentar o ciclo de vida útil e a resistência à corrosão. As morfologias das estruturas de solidificação, caracterizadas principalmente por arranjos celulares e dendríticos, e suas grandezas representadas por espaçamentos celulares e dendríticos controlam a distribuição de soluto, segundas fases dentro das regiões intercelulares ou interdendríticas, que determinam as propriedades finais. O comportamento mecânico e as características estruturais dos componentes de bateria têm papel importante no desempenho das baterias. O presente trabalho pretende contribuir para o entendimento do desenvolvimento microestrutural de ligas diluídas do sistema Pb-Sn (Pb-1,0%Sn e Pb-2,5%Sn) que possuem elevada importância para a indústria na fabricação de componentes de baterias automotivas e estacionárias. Os experimentos de solidificação realizados em dispositivo no qual o calor é extraído somente pelo sistema de resfriamento a água, localizado na base do conjunto lingote/lingoteira (solidificação ascendente). As variáveis térmicas de solidificação foram determinadas a partir do registro de temperaturas de termopares posicionados dentro da lingoteira em diferentes posições em relação à superfície refrigerada do lingote. Amostras das mencionadas ligas Pb-Sn foram utilizadas para analisar as influências das variáveis térmicas de solidificação e da concentração de soluto nas macro e microestruturas resultantes e na resistência mecânica. Foram determinados os limites de resistência à tração e alongamentos específicos em função do espaçamento celular e a influência da microestrutura no comportamento eletroquímico foi avaliada por intermédios dos ensaios de espectroscopia de impedância eletroquímica, extrapolação de Tafel, curvas de polarização e análise por circuito equivalente em solução eletrolítica de ácido sulfúrico. Observou-se que a resistência a corrosão diminui e o limite de resistência a tração aumenta com a diminuição do espaçamento celular.
Abstract: Lead-acid batteries manufacturers have modified the manufacturing processes and the chemical composition of alloys used in battery grids in order to decrease their weight as well as to reduce the production costs, and to increase the battery life-time cycle and the corrosion-resistance. The morphological microstructures characterized by cellular and dendritic arrays and its correspondents cellular and dendrite arm spacings control the solute distribution, second phases in the intercellular and interdendritic regions affecting the resulting properties. The mechanical behavior and microstructural characteristics of lead-acid battery components have an important role in the battery performance. The present work aims to contribute to the understanding of the microstructural development of dilute Pb-1,0 wt.%Sn and Pb-2.5 wt.%Sn alloys which are widely applied in the manufacturing of automobile and stationary lead-acid batteries. A water-cooled vertical upward unidirectional solidification system was used to obtain the samples. The experimental set-up was designed in such a way that the heat was extracted only through the water-cooled bottom, promoting upward directional solidification. Thermal readings were obtained by thermocouples positioned at different distances from the heat-extracting surface at the casting bottom. Pb-Sn alloy samples were used to analyze the effects of the thermal solidification variables and solute content on the resulting macro and microstructures and on the mechanical properties. The ultimate tensile strength and the elongation were determined as a function of the cellular arm spacing. The effect of the resulting microstructure on the electrochemical corrosion behavior was also analyzed based on electrochemical parameters, determined by Tafel plots, polarization curves and an equivalent circuit analysis after corrosion tests carried out in a sulphuric acid solution. It was observed that the corrosion resistance decreases and the ultimate tensile strength increases with decreasing cellular spacing.
Mestrado
Materiais e Processos de Fabricação
Mestre em Engenharia Mecânica
31
Santos, Tiago Felipe de Abreu. "Avaliação microestrutural e de desempenho de juntas soldadas de aços inoxidáveis duplex por atrito com pino não consumível." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263414.
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Orientador: Antonio Jose Ramirez LondonoTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: Juntas consolidadas a topo com penetração completa, livres de defeitos, foram obtidas usando a técnica de soldagem por atrito com pino não consumível em chapas de 6 mm de espessura para os aços inoxidáveis duplex UNS S32101 e S32205 e os superduplex UNS S32750 e S32760. Testes de dobramento de raiz indicaram a penetração completa e a ausência de trincas bem como inspeção por líquido penetrante. A penetração completa foi atingida quando o aporte energético aumentou de 0,89 kJ/mm para 1,43 kJ/mm. Os testes de tração na junta soldada evidenciaram a falha no MB e o aumento da resistência mecânica da junta associada à uma boa ductilidade, exceto para o UNS S32760. Mapas de dureza mostraram o aumento da dureza em toda junta soldada em relação ao metal de base. Avaliação microestrutural mostrou um pronunciado refinamento do tamanho de grão médio de ambas as fases (ferrita e austenita) na junta soldada para os materiais estudados. A avaliação por microscopia de transmissão indicou a evolução de arranjos celulares formando contornos de grão na ferrita corroborando o mecanismo de recuperação e rescristalização dinâmica contínua. Análise por meio da técnica de EBSD mostrou elevada fração de contornos de grão do tipo 'sigma' na 'gama' indicando a recristalização dinâmica descontínua desta fase. Os AID S32205, S32750, S32760 mostraram sutis alterações na resistência à corrosão para meios com diferentes concentrações de cloretos (3,5% NaCl e 1 M NaCl). Porém, para concentrações mais altas o AISD S32760 exibiu importante decréscimo de resistência a corrosão. Este comportamento foi associado à maior fração de ferrita e a precipitação do nitreto de cromo na junta soldada. O AID S32101 mostrou diminuição da resistência à corrosão na condição como soldado
Abstract: Fully consolidated and full penetration butt joints were produced using friction stir welding (FSW) on 6 mm thick plates of UNS S32101 lean duplex stainless steel (LDSS), S32205 duplex stainless steel (DSS) and S32750 and S32760 superduplex stainless steels (SDSS) with heat input of 1.43 kJ/mm. Liquid penetrant inspection showed the full penetration obtained in the welded joints which was corroborated with the bending tests. Transverse tensile tests of the welded joints failed at the base metal revealing an overmatching weld metal. Moreover, longitudinal tensile tests of the welded joints presented an increase of the yield and tensile strength for all joints together with the elongation, but for UNS S32760, which showed a ductility reduction. Microhardness revealed a hardness increase for all the joints, while the SDSSs presented a more homogeneous hardeness areas of joint. Microstructural evaluation indicated a pronounced grain refinement in the welded joints for all the studied materials achieving down to 1 ?m grain size. Transmission electron microscopy and EBSD indicated dislocation cells evolving towards grain boundaries that corroborates the occurrence of dynamic recovery followed by continuous dynamic recrystallization for ferrite. Austenite exhibited high fraction of high angle grain bondaries associated with 'sigma' boundaries indicating the discontinuous dynamic recrystallization. DSS UNS S32205, SDSS UNS S32750, and S32760 showed good corrosion behavior for 3.5% NaCl and 1 M NaCl environments. However, with the increase of chlorides concentrations, the SDSS UNS S32760 exhibited strong decrease of corrosion performance. This behavior was associated with a combination of high ferrite fraction and chromium nitride precipitation. DSS S32101 exhibited a decrease of corrosion performance when welded
Doutorado
Materiais e Processos de Fabricação
Doutor em Engenharia Mecânica
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BUGARIN, ALINE de F. S. "Estudo da resistência à corrosão das ligas de alumínio 2024-T3 e 7475-T651 soldadas por fricção e mistura (FSW)." reponame:Repositório Institucional do IPEN, 2017. http://repositorio.ipen.br:8080/xmlui/handle/123456789/28030.
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Submitted by Pedro Silva Filho (pfsilva@ipen.br) on 2017-11-21T11:56:39Z
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O processo de soldagem por fricção e mistura (FSW) tem despertado grande interesse nos últimos anos e tornou-se uma alternativa para unir materiais de baixa soldabilidade, como as ligas de alumínio das séries 2XXX e 7XXX, as quais são empregadas na estrutura das aeronaves, por possuírem elevada relação resistência/peso. O processo FSW, todavia, causa mudanças microestruturais nos materiais soldados, particularmente na zona misturada (ZM) e nas zonas termicamente (ZTA) ou termomecanicamente (ZTMA) afetadas. Estas mudanças geralmente interferem no desempenho frente à corrosão das ligas soldadas. No presente estudo, a resistência à corrosão das ligas de alumínio 2024-T3 e 7475-T761, unidas pelo processo FSW foi investigada em solução 10 mM de NaCl. Ensaios de visualização em gel ágar-ágar e de imersão associados a técnicas microscópicas foram realizados para investigar o efeito do acoplamento galvânico na corrosão das diferentes regiões da junta soldada. Os resultados do ensaio de visualização em gel mostraram que, quando acopladas, a liga 2024 atua como cátodo e a 7475 como ânodo. Os ensaios de imersão revelaram acoplamento galvânico entre as ligas na zona misturada (ZM). A região mais afetada pela corrosão foi a ZTMA da liga 7475, com corrosão intergranular desde as primeiras horas de imersão. A influência do processo de soldagem na resistência à corrosão das duas ligas de alumínio foi investigada por ensaios eletroquímicos. Os ensaios eletroquímicos adotados foram medidas de potencial de circuito aberto (PCA) em função do tempo de exposição ao meio corrosivo, espectroscopia de impedância eletroquímica (EIE) e curvas de polarização potenciodinâmica. Os ensaios de polarização mostraram elevada atividade eletroquímica na zona de mistura indicada pelos altos valores de densidade de corrente em comparação com as demais zonas testadas. Os resultados de EIE globais mostraram que nas primeiras horas de exposição ao eletrólito o processo de corrosão foi predominantemente controlado pela liga 7475; todavia, com o tempo de exposição ao eletrólito, a corrosão passou a ser controlada pela liga 2024.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
33
Xu, Nan Materials Science & Engineering Faculty of Science UNSW. "Corrosion behaviour of aluminised steel and conventional alloys in simulated aluminium smelting cell environments." Awarded by:University of New South Wales. School of Materials Science & Engineering, 2002. http://handle.unsw.edu.au/1959.4/18760.
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Aluminium smelting is a high temperature electrometallurgical process, which suffers considerable inefficiencies in power utilization and equipment maintenance. Aluminium smelting cell works in the extreme environments that contain extraordinarily aggressive gases, such as HF, CO and SO2. Mild steel used as a structural material in the aluminium industry, can be catastrophically corroded or oxidized in these conditions. This project was mainly concerned with extending the lifetime of metal structures installed immediately above the aluminium smelting cells. An aluminium-rich coating was developed on low carbon steel A06 using pack cementation technique. Yttria (Y2O3) was also used to improve the corrosion resistance of coating. Kinetics of the coating formation were studied. XRD, FESEM and FIB were employed to investigate the phase constitution and the surface morphology. Together with other potentially competitive materials, aluminium-rich coating was evaluated in simulated plant environments. Results from the long time (up to 2500h) isothermal oxidation of materials at high temperature (800??C) in air showed that the oxidation resistance of coated A06 is close to that of stainless steel 304 and even better than SS304 in cyclic oxidation tests. Coated A06 was also found to have the best sulfidation resistance among the materials tested in the gas mixture contains SO2 at 800??C. Related kinetics and mechanisms were also studied. The superior corrosion resistance of the coated A06 is attributed to the slow growing alpha-Al2O3 formed. Low temperature corrosion tests were undertaken in the gas mixtures containing air, H2O, HCl and SO2 at 400??C. Together with SS304 and 253MA, coated A06 showed excellent corrosion resistance in all the conditions. The ranking of the top three materials for corrosion resistance is: 253MA, coated A06 and SS304. It is believed that aluminised A06 is an ideal and economical replacement material in the severe corrosive aluminium smelting cell environment.
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MARQUES, ROGERIO A. "Estudo da resistência à corrosão do aço inoxidável ferrítico AISI 444 para aplicação como biomaterial." reponame:Repositório Institucional do IPEN, 2014. http://repositorio.ipen.br:8080/xmlui/handle/123456789/26397.
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Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2016-06-22T14:30:57Z
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Tese (Doutorado em Tecnologia Nuclear)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
35
Swartz, Natasja Alexandria. "Rational Design of Materials for the Protection of Outdoor Metalworks." PDXScholar, 2015. https://pdxscholar.library.pdx.edu/open_access_etds/2488.
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Protective coatings are commonly used to protect culturally significant works, such as outdoor sculptures and architectural elements. Given the valuable nature of such metalworks, there is a surprising lack of environmentally sustainable coatings available for their conservation. High performance clear coatings are not developed or thoroughly tested for compatibility and longevity on outdoor sculptures. This can make the implementation of both methods and materials, no matter how promising in a lab, a significant hurdle for the conservation science community. This dissertation work initially aims to replace high-VOC formulations such as acrylic lacquers and waxes currently used as protective coatings for bronze with a waterborne coating by investigating the film formation differences between coating types. Such differences likely have implications for initial film barrier properties as well as long-term performance.
For coating any large-scale metal object, cost-effectiveness limits applicable coatings to commercially available resins with some minor adjustments. Additional requirements for protective coatings for artwork require they must also be transparent, reversible, easily applied and environmentally sustainable. The chemical and physical properties of polymeric coatings with nanoclays modifiers were investigated as they may offer superior weatherability and act as better barriers to water absorption than commonly used lacquers and waxes. This work ultimately finds that nanocomposites with poly(vinylidene fluoride) latex and chemically stabilized nanoclays significantly improved performance and may be a viable option in the protection of material cultural heritage. Protection of high value objects where aesthetics is also important, such as airplanes, buildings, and sculptures are among the possible applications for this research.
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Soiné, Robert Paul. "An analysis of the performance of a South African stainless steel manufacturer in localising the demand for corrosion resistant steels within the Eastern Cape catalytic converter industry." Thesis, Port Elizabeth Technikon, 2004. http://hdl.handle.net/10948/200.
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Commercial decisions are been made with respect to the competitive advantage of manufacturing catalytic converters in South Africa. This thesis identifies those factors relating to the sourcing of stainless steel and the impact it has of securing future business in a competitive environment. The catalytic converter industry requires the support of a stainless steel plant that provides high quality products at a competitive price, while keeping abreast with international developments.
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Akhtar, Mst Alpona. "Hydrophobicity of Magnetite Coating on Low Carbon Steel." Thesis, University of North Texas, 2018. https://digital.library.unt.edu/ark:/67531/metadc1248389/.
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Superhydrophobic coatings (SHC) with excellent self-cleaning and corrosion resistance property is developed on magnetite coated AISI SAE 1020 steel by using a simple immersion method. Roughness measurement, scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), contact angle measurement (CAM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), potentiodynamic polarization test, electrochemical impedance spectroscopy (EIS), and qualitative characterization of self-cleaning behavior, antifouling property and durability of the coatings are assessed. A water contact angle as high as 152o on the coated surface with excellent self-cleaning and resistivity to corrosion and good longevity in atmospheric air is obtained. Self-cleaning test results prove that these surfaces can find applications in large scale production of engineering materials. Potentiodynamic polarization tests and EIS tests confirm that the superhydrophobic low carbon steel surfaces have better resistance to corrosion compared to bare steel and magnetite coated steel in 3.5% NaCl solution. But the longevity of the coated steel surfaces in 3.5% salt solution is limited, which is revealed by the immersion durability test. However, hydrophobic coatings (HC) have better stability in normal tap water, and it can stay unharmed up to 15 days. Finally, hydrophobic coatings on low carbon steel surface retains hydrophobic in open atmosphere for more than two months. Results of this investigation show surface roughness is a critical factor in manufacturing hydrophobic steel surfaces. Higher contact angles are obtained for rougher and more uniform surfaces. A linear mathematical relationship (y =6x+104; R2 = 0.93) is obtained between contact angle (y) and surface roughness (x).
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Saillard, Audric. "Modeling and simulation of stress-induced non-uniform oxide scale growth during high-temperature oxidation of metallic alloys." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33898.
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The metallic alloys employed in oxidizing environment at high temperature rely on the development of a protective oxide scale to sustain the long-term aggressive exposition. However, the oxide scale growth is most of the time coupled with stress and morphological developments limiting its lifetime and then jeopardizing the metallic component reliability. In this study, a mechanism of local stress effect on the oxidation kinetics at the metal/oxide interface is investigated. The objective is to improve the understanding on the possible interactions between stress generation and non-uniform oxide scale growth, which might result in a precipitated mechanical failure of the system. Two different oxides are studied, alumina and chromia, in two different industrial systems, thermal barrier coatings and solid oxide fuel cell interconnects. A specific thermodynamic treatment of local oxide phase growth coupled with stress generation is developed. The formulation is completed with a phenomenological macroscopic framework and a numerical simulation tool is developed allowing for realistic analyses. Two practical situations are simulated and analyzed, concerning an SOFC interconnect and a thermal barrier coating system, for which oxide scale growth and associated stress and morphological developments are critical. The consequence of the non-uniform oxide growth on the system resistance to mechanical failure is investigated. Finally, the influences of material-related properties are studied, providing optimization directions for the design of metallic alloys which would improve the mechanical lifetime of the considered systems.
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Chen, Xi. "Corrosion Resistance Assessment of Pretreated Magnesium Alloys." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1282837277.
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Gatzanis, Gustav Ernest. "Abrasion-corrosion and stress corrosion resistance of a 9Cr-2Ni-0.7Mo steel in simulated mine water." Master's thesis, University of Cape Town, 1991. http://hdl.handle.net/11427/21957.
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Bibliography: pages 101-109.The locally (RSA) developed 9Cr-2Ni-0.7Mo steel designated 927 formed the subject of this study. Its abrasion-corrosion and stress corrosion performances were assessed in laboratory tests simulating the underground environment in South African gold mines. The results indicate that the alloy performs favourably in abrasive-corrosive applications, outperforming several other higher chromium containing steels which have been designed for the purpose. The alloy is also highly resistant to sec at free corrosion potential in simulated mine water. The good abrasion-corrosion resistance is attributed to the adequate corrosion resistance of the alloy acting in conjunction with the favourable combination of strength and toughness afforded the alloy by its fine grain size and microduplex microstructure of martensite and interlath retained austenite. The production variables of plate thickness and prior cold working were found to exert negligible influence on corrosion-abrasion resistance. This is ascribed to the small influence of these processes on the hardness and associated mechanical properties due the inherent low work hardening ability of the alloy. Slow strain rate (SSR) stress corrosion cracking tests were performed on the alloy in four microstructural conditions viz. as-rolled, tempered, welded and post weld heat treated. The material showed an immunity to sec in all the microstructural conditions for tests conducted at open circuit potential. This apparent immunity is attributed to the difficulty in initiating sec by pitting on the plain specimens over the relatively short test durations. Polarisation to extreme cathodic potentials (-1200m V) resulted in hydrogen embrittlement of this high strength alloy with failure predominantly along prior austenite grain boundaries. Anodic potentials in the excess of OmV induced tunnel-like corrosion pitting attack. Fractographical evidence of sec at the base of these pits indicates the development of the conditions necessary for sec within the pit confines. This is cited as evidence in support of the hypothesis of sec initiation difficulty.
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Brisenmark, Emil, and Valencik Jane Jönsson. "Evaluation of the Effect of Non-Metallic Inclusions on the Corrosion Resistance of Stainless Steels and Nickel-based Alloys." Thesis, KTH, Materialvetenskap, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-277900.
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Non-metallic inclusions (NMI) are small impurities that can always be found in steel and other materials. NMIs are of great importance because they may negatively impact various properties of the steel, depending on their composition, morphology and numbers. In the oil and gas industry, one of the most concerning property that can be affected by the NMIs is corrosion resistance. In this report, certain aspects of NMIs were investigated, such as size or composition and effect which they have on the corrosion resistance. To accomplish this, two different steel alloy samples from pipelines were analyzed using electrolytic extraction,a scanning electron microscope (SEM) and a software called ImageJ. The results showed that only Niobium-Titanium carbides (NbTi-C) which were found on one of the samples had the potential to be dangerous, due to them causing pits ranging from 1 to 12.5 times their inclusion size. It was also found out that the size of the inclusions did not affect the size of the pitting that they caused.Icke metalliska inneslutningar (NMI) är små föroreningar som alltid finns i stål och andramaterial. NMI:er är mycket viktiga eftersom de kan negativt påverka olika egenskaper hos stål, beroende på deras komposition, morfologi och antal. I olje -och gasindustrin är en särskilt oroande egenskap som kan påverkas av NMI:er deras korrosionsmotstånd. I denna rapport undersöktes hur olika aspekter hos NMI:er, som storlek eller komposition, påverkade korrosionsmotståndet i rostfritt stål. För att utföra detta analyserades två olika stållegeringsprovbitar från pipelines med elektrolytisk extraktion, ett svepelektronmikroskop (SEM) och ett program som kallas ImageJ. Från resultatet framkom det att baraNiob-Titankarbider (NbTi-C) som fanns på en av provbitarna hade potentialen att vara farlig, då den orsakar gropar som är 1 till 12.5 gånger större än sin egen storlek. Det framkom också att storleken på inneslutningarna inte påverkade storleken på deras gropar.
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Nunez, Moran Emerson Osvaldo. "Evaluation of the Localized Corrosion Resistance of 21Cr Stainless Steels." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1279854886.
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Knutsen, Robert Douglas. "A microstructural examination of duplex ferrite -martensite corrosion resisting steels." Doctoral thesis, University of Cape Town, 1989. http://hdl.handle.net/11427/26079.
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This thesis reports a study of the microstructural evolution of chromium containing duplex ferrite-martensite steels and examines the effects of the microstructure on the mechanical properties. Emphasis has been placed on determining the microstructural factors responsible for the persistent occurrence of anisotropy in a modified 12 wt% Cr steel designated 3CR12. in addition an investigation has been carried out in order to refine the grain structure of a ferritic steel containing 16-17 wt % Cr by inducing a duplex ferrite-martensite phase structure. The microstructural evolution of 3CR12 was studied during cooling from a solution heat treatment at 1380°C and the natures of the phase transformations evident were investigated. Energy dispersive X-ray spectroscopy (EDS), in association with a scanning electron microscope (SEM), was used to determine the composition of the phases arising from the solid state δ-ferrite to austenite transformation. It is shown that the high temperature δ-ferrite phase partially decomposes to austenite via a Widmanstatten growth mechanism and consequently a banded two phase structure is produced after hot rolling. The element partitioning which arises during the solid state δ-ferrite decomposition ieads to compositional banding with an indelible nature. A model is proposed for the events leading to the generation of the banded phase structure and the formation of an elongated ferritic microstructure in 3CR12 after sub-critical annealing. The type and distribution of non-metallic inclusions occurring in 3CR12 has also been assessed. Characteristic fracture modes developed during impact testing have been related to the grain morphology and the occurrence of non-metallic inclusions. It is shown that splits form parallel to the rolling plane when Charpy specimens are subjected to impact testing and that both impact energy and mode of fracture are dependent on the directional properties of the 3CR12 microstructure. Splitting is predominantly caused by the low energy crack path provided by long, undulating grain boundaries parallel to the rolling plane, and inclusions, particularly manganese sulphides (MnS), facilitate low energy modes of fracture associated with the splitting phenomenon. MnS inclusions are also found to affect the corrosion resistance of 3CR12 and careful control of the chemistry of the steel permits these inclusions to be restricted to levels at which acceptable impact and corrosion properties are maintained. Refinement of the grain structure of ferritic steels containing 16-17 wt % Cr was carried out by modifying the ratio of ferritising elements to austenitising elements in the steel chemistry. Suitable ruckel additions have been determined which provide alloys with sufficient austenitising ability to refine the high temperature δ-ferrite phase and consequently a duplex ferrite-martensite microstructure is produced. Tempering of these alloys at 700°C results in a lamellar ferrite-martensite structure which gives rise to an attractive combination of impact and tensile properties which may provide a stainless steel with superior cost effectiveness to austenitic grades.
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Wentzel, Eduard John. "Erosion-corrosion resistance of tungsten carbide hard metals with different binder compositions." Master's thesis, University of Cape Town, 1995. http://hdl.handle.net/11427/18212.
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A study has been made of the slurry erosion resistance of a series of cemented tungsten carbides with different binder compositions consisting of combinations of cobalt, nickel and chromium. Testing was carried out on a specially designed laboratory rig in both tap and salt water using silica sand as an erodent. The synergistic action of erosion and corrosion on WC hard metals results in greatly enhanced wear rates compared to either erosion or corrosion processes alone. Cemented carbides with a 1 0 wt% binder were found to have a better slurry erosion resistance than the corresponding 6 wt% binder grades or the pure metal binder alloys alone. The performance of all the materials was found to be much worse in a salt water medium compared to tap water. The alloying of either pure Nickel or Cobalt binders was found to influence the fracture properties and corrosion resistance and lead to an improvement in the slurry erosion resistance of the cemented carbides. However any improvement in the corrosion resistance of the binder did not directly enhance the slurry erosion resistance of the cermet. Explanations are advanced to explain these differences in behaviour linked to chemical composition, mechanical properties of the binder phase and the dynamic nature of the slurry erosion system. Comparisons are also made between the performance of the Ni-Cr-Co based cermets and the pure alloyed metal binder grades. The acceptability of modelling the slurry erosion and corrosion resistance of cermets based on the behaviour of the binder phase materials is discussed.
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Zhu, Liu. "Surface modification of materials using high power lasers and an arc image intensifier." Thesis, University of Liverpool, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316624.
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Solem, Benjamin, Ante Vallien, and Philip Wernstedt. "Applying Thermal Diffusion Galvanization on Wood Screws : Effects on Corrosion Resistance and Mechanical Properties." Thesis, KTH, Materialvetenskap, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-205234.
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Today, fastening articles such as screws and nails are treated with different surface coatings to withstand corrosion. The Swedish distributor ESSVE® Produkter AB uses a nano coating called CorrSeal™ for high corrosion protection of their screws. Thermal diffusion galvanization (TDG) is a more environmentally friendly method that the company seeks to use as replacement for the current treatment. This process of zinc diffusion is carried out at around 400 °C for several hours. The aim of the project is to investigate the possibility to surface treat a wood screw using TDG. The elevated temperature is suspected to decrease the hardness of the hardened screw. Therefore, a hardened and tempered screw without surface treatment is sent to a TDG facility. Industrial furnaces are used for similar heat treatments of screws with different hardenings. Both processes are analyzed by evaluating the results of hardness, bending, and microscopy. No immediate correlation between the TDG process and heat treatment in the industrial furnaces is found. Results show that the tested screws softened to a higher degree in the TDG process compared to treatment in the industrial furnaces. The mechanical properties of the tested screws, after the TDG process, are not acceptable. The zinc layer thickness on the screws is uneven yet believed to meet the required demands on corrosion resistance. Results also show that incorporating the TDG process in the tempering step is essential to meet the demands on hardness. Additionally, changing the composition of the material can lead to higher resistance against softening at the elevated temperatures. Further research is however needed to present a screw with sufficient corrosion resistance from the TDG process that will meet the demandson hardness and bending.
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Steneteg, Jakob. "Corrosion Resistant Multi-Component Coatings for Hydrogen Fuel Cells." Thesis, Linköpings universitet, Tunnfilmsfysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-174617.
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Multi-component coatings and high entropy alloys have in recent years attracted great interest for research, since they have shown to exhibit properties greater than the com- ponents of their parts. Today’s climate challenges requires transitioning from fossil fuels to renewable energy sources which demands use of new technology and new innovations. The hydrogen fuel cell is a technology which produces no carbon emissions, and the drive for innovation has led researchers to apply multi-component (high entropy alloys) coatings to invent the next generation hydrogen fuel cells and help the transition to renewable energy sources. This thesis has investigated the process-structure-property relationships of four deposi- tion growth parameters: target current (Itarget), argon pressure (PAr). substrate bias (Vsubstrate) and deposition time (tdeposition) on TiNbZrTa-coatings, grown by magnetron sputtering using an industrial deposition system. The range of the parameters have been: Itarget from 2.5 to 6 A, PAr from 1 to 17 mTorr, Vsubstrate from 30 to 200 V and tdeposition from 3.6 to 12 minutes (depending on Itarget). Coatings have been grown on Si (001) and stainless steel 304 and 316L substrates. The coating microstructure was analyzed by X-ray diffraction and electron microscopy. The results have yielded that all coatings are equimolar and that the coatings exhibit three different morphologies, two different topologies and two different corresponding structures. The different morphologies are wave, coarse columnar and fine columnar morphology. The two topologies are nodular and dune surface topology. The two different structures are a solid solution BCC (110) phase and an amorphous or nanocrystalline phase. The results indicate that parameters affecting the temperature of the substrate (Tsubstrate) is the prime decider for the final morphology of the coatings. High Itarget and Vsubstrate, low PAr and long tdeposition all increases Tsubstrate and results in a coating which exhibits a fine columnar morphology, dune topology and a solid solution BCC phase. These types of coatings have also proven to have improved corrosion resistance compared to the other type of coatings seen in this thesis. The other kind of coating is grown with low Itarget and Vsubstrate, high PAr and short tdeposition, which causes minimal increase of Tsubstrate. These growth parameters result in a coating with coarse columnar morphology, nodular topology and amorphous or nanocrystalline phase, with less corrosion resistance.FunMat II
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Örnberg, Andreas. "Study of Electrochemical Behaviour and Corrosion Resistance of Materials for Pacemaker Lead Applications." Licentiate thesis, KTH, Chemistry, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4650.
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For patients suffering bradycardia, i.e., too slow heart rhythm, the common treatment is having a pacemaker implanted. The pacemaker system consists of the pacemaker and a pacing lead. The pacing lead is connected to the pacemaker and at the other end there is a stimulation electrode. The most common conductor material is a cobalt-based super alloy (MP35N® or 35N LT®), with the main constituents Ni, Co, Cr and Mo. The pacemaker electrode is often made of a substrate material with a rough surface coating. The substrate materials are predominantly platinum/iridium alloy and titanium. The material choice is of great importance for the performance and stability during long-term service. Excellent corrosion resistance is required to minimize elution of metal ions in the human body.
In this thesis, the electrochemical behaviour and corrosion resistance of the Co-based alloys and Ta (as electrode substrate), in a phosphate buffer saline (PBS) solution with and without addition of H2O2, was investigated by means of potentiodynamic polarization, cyclic voltammetry, electrochemical impedance spectroscopy and simulated pacemaker pulsing. The metal release from the Co-based alloy during the passivation treatment and exposure in the synthetic biological media was measured by using inductive coupled plasma - atomic emission spectroscopy (ICP-AES). Moreover, surface composition was analyzed by using x-ray photoelectron spectroscopy.
The results show that the chemical passivation of Co-based alloy 35N LT® increased the corrosion resistance and reduced Co release significantly, even in more hostile environment, i.e. PBS with addition of H2O2. The increased corrosion resistance is due to the Cr enrichment in the surface layer. The reduced Co release is due to a preferential dissolution of Co from the surface oxide layer during the chemical passivation. The electrochemical investigation of uncoated and rough TiN coated Ta show that uncoated Ta is not suitable electrode material due to formation of a highly resistive surface oxide film. Whereas the rough TiN coated Ta exhibits desirable electrochemical performance for pacemaker electrodes. The addition of H2O2 in the PBS has a large influence on the electrochemical behaviour of Ta, but the influence is small on the rough TiN coated Ta.
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Örnberg, Andreas. "Study of electrochemical behaviour and corrosion resistance of materials for pacemaker lead applications /." Stockholm : Kemi, Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4650.
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Davies, David Phillip. "Fatigue behaviour of gas-carburised, temper-resistant, low-alloy steels." Thesis, University of Liverpool, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321168.
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