Articoli di riviste: "Stainless steels's etching"

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Fedorov, Aleksandr Sergeevich, Andrey Igorevich Zhitenev, Darya Andreevna Strekalovskaya, Aleksandr Aleksandrovich Kur e Alexey Aleksandrovich Alkhimenko. "Quantitative Description of Duplex Stainless Steels Microstructure Using Selective Etching". Metals 11, n. 11 (31 ottobre 2021): 1750. http://dx.doi.org/10.3390/met11111750.

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The properties of duplex stainless steels (DSSs) depend on the ferrite–austenite ratio, on the content of secondary phases and on the contamination with non-metallic inclusions. To assess the quality of DSSs, it is necessary to use an integrated approach which includes controlling for the volume fraction, the morphology and the distribution of all phases and non-metallic inclusions. Samples of several grades of DSSs were obtained using various heat treatments, such as solution annealing and quenching from 1050 to 1250 °C to obtain different amounts of ferrite and to provoke annealing at 850 °C to precipitate σ-phase. As a result, a metallographic technique of phase analysis in DSSs based on selective etching and subsequent structure parameters estimation according to ASTM E1245 was developed. We demonstrated that the developed method of quantitative analysis based on selective etching and metallographic analysis according to ASTM E1245 allows us to obtaining much more accurate results, compared to the point count method described in ASTM E562 and to the XRD method.

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Irgolič, Tomaž, David Potočnik, Mirko Ficko e Peter Kirbiš. "Microstructural characterization of laser cladded AISI 316 stainless steel on a carbon steel substrate". Advanced Technologies & Materials 44, n. 2 (20 dicembre 2019): 1–5. http://dx.doi.org/10.24867/atm-2019-2-001.

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Laser engineering net shaping (LENS) is a method of depositing metals into fully shaped parts or for the production of clad layers of noble or wear resistant metals on construction grade steels. In the current work stainless steel was deposited using different combinations of processing parameters such as speed, layer thickness and laser power. The resulting microstructures within the clad layers were then characterized using different etching techniques. Microstructures formed during the SLM process are comprised of columnar grains with a cellular, cellular/dendritic substructure. The exact shape of these grains is difficult to observe with the use of common etching techniques, this is especially true when considering thin cladded layers, with dissimilar etching behavior. For this purpose we compared a variety of different etchants, which attack the ferrite phase or produce a tint effect. Special attention was giving to the delineation of the columnar grains, which under certain processing parameters can exceed the thickness of individual deposited layers.

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Baghra, Chetan, Aniruddha Kumar, D. B. Sathe, R. B. Bhatt, P. G. Behere e Mohd Afzal. "Laser etching of austenitic stainless steels for micro-structural evaluation". Optics & Laser Technology 69 (giugno 2015): 172–79. http://dx.doi.org/10.1016/j.optlastec.2015.01.002.

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David, Charles, Fiona Ruel, Florent Krajcarz, Clément Boissy, Saghi Saedlou e Vincent Vignal. "Effect of Grain Size on the Anodic Dissolution of Lean Duplex UNS S32202 Austenitic-Ferritic Stainless Steel". Corrosion 75, n. 12 (30 settembre 2019): 1450–60. http://dx.doi.org/10.5006/3218.

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The effect of grain size on the anodic dissolution of lean duplex UNS S32202 dual-phase austenitic-ferritic stainless steel was evaluated. Grain coarsening was achieved by heat treatment, and grain size and grain boundary densities determined by automatic image analysis after etching. Potentiodynamic electrochemical testing in acidic chloride medium allowed isolating the anodic dissolution behavior of the crystallographic phases of the material. A relationship between grain boundary density (for grain sizes in the micrometer range) and dissolution rate has been found, showing that reducing grain size enhances active corrosion rates in environments that promote active behavior. This leads to new possibilities of industrial adjustment of the corrosion behavior of duplex stainless steels via grain size control.

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Fedorov, Aleksandr, Andrey Zhitenev, Darya Strekalovskaya e Aleksandr Kur. "Quantitative Description of the Microstructure of Duplex Stainless Steels Using Selective Etching". Materials Proceedings 3, n. 1 (8 marzo 2021): 4. http://dx.doi.org/10.3390/iec2m-09387.

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: The properties of duplex stainless steels (DSSs) depend on the ferrite–austenite ratio and on the contents of secondary phases. Therefore, it is necessary to control the volume fractions, morphologies, and distribution patterns of all phases. The phases in the samples were identified using thermodynamic modeling and scanning electron microscopy. Investigated specimens were obtained after different heat treatments, such as solution annealing and quenching from 1050 to 1250 °C to obtain different amounts of ferrite and annealing at 850 °C to precipitate the σ-phase. Therefore, a metallographic technique for assessing the phases in DSSs based on selective etching and subsequent analysis according to ASTM E 1245 was developed. It was shown that the developed method of quantitative analysis based on selective etching and metallographic assessment according to ASTM E 1245 allows obtaining much more accurate results compared to the proposed ASTM E 562 method, which correlates well with the XRD quantitative phase analysis.

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Tolnai, Ferenc, e Balázs Varbai. "Effect of Heat Treatment on the Microstructure of Duplex Stainless Steel Welds". Acta Materialia Transylvanica 3, n. 2 (1 ottobre 2020): 103–7. http://dx.doi.org/10.33924/amt-2020-02-10.

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Abstract Duplex stainless steels (DSS) are gaining in popularity due to their characteristic features, excellent mechanical properties, and corrosion resistance. The microstructure of DSSs consists of ferrite up to 50 %, and the rest is built up from austenite. The ferritic microstructure can cause chromium-nitride precipitation because the nitrogen solubility in the ferrite phase is very low below 700 °C. Our research showed that electrochemical etching is an acceptable process for revealing chromium-nitrides. Additionally, our research points out that chromium-nitride acts as a secondary austenite nucleation site.

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Nakasa, Keijiro, Akihiro Yamamoto, Rongguang Wang e Tsunetaka Sumomogi. "Formation of Fine Protrusions by Sputter Etching of Martensitic Stainless Steels". Tetsu-to-Hagane 100, n. 5 (2014): 647–55. http://dx.doi.org/10.2355/tetsutohagane.100.647.

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Potgieter, J. H., e P. de Visser. "Potentiostatic etching of duplex stainless steels and high chromium white cast irons". Materials Science and Technology 9, n. 4 (aprile 1993): 336–42. http://dx.doi.org/10.1179/mst.1993.9.4.336.

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NAKASA, Keijiro, Xu YAN, Masashi YOSHIDA e Tsunetaka SUMOMOGI. "Deformation Characteristics of Fine Protrusions Formed by Sputter-Etching of Stainless Steels". Journal of Solid Mechanics and Materials Engineering 4, n. 7 (2010): 1103–10. http://dx.doi.org/10.1299/jmmp.4.1103.

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Villalobos Vera, Doris Ivette, e Ivan Mendoza Bravo. "Effect of annealing temperature on the microstructure of hyperduplex stainless steels". Ingeniería Investigación y Tecnología 20, n. 2 (1 marzo 2019): 1–6. http://dx.doi.org/10.22201/fi.25940732e.2019.20n2.024.

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Samples of hyperduplex stainless steels were produced experimentally and exposed to different conventional annealing heat treatments in order to obtain the microstructural balance of 50% ferrite and 50% austenite. To differentiate the ferrite and austenite from any secondary phase, selective etching was used and quantitative metallography was performed to measure the percentage of phases. Results showed that conventional annealing heat treatments promote the transformation from ferrite to sigma phase and secondary austenite, suggesting a higher occurrence of sigma phase in the experimental hyperduplex alloys compared to other duplex alloys due to the superior content of chromium and molybdenum. On the other hand, a balanced microstructure free of secondary phases was accomplished increasing the temperature of the annealing heat treatment, which allowed the transformation of ferrite into austenite during cooling.

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Choe, Byung Hak, Sang Woo Lee, Jong Kee Ahn, Jinhee Lee e Tae Woon Lim. "Hydrogen Induced Cracks in Stainless Steel 304 in Hydrogen Pressure and Stress Corrosive Atmosphere". Korean Journal of Metals and Materials 58, n. 10 (5 ottobre 2020): 653–59. http://dx.doi.org/10.3365/kjmm.2020.58.10.653.

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The phenomena of hydrogen induced cracking (HIC) in 304 stainless steels was considered in a hydrogen pressure and stress corrosive atmosphere. Microstructures with chloride pits and stress corrosion cracks around the HIC were analyzed by SEM/EDS. Abnormal phase transformations induced by the hydrogen were analyzed using TEM and diffraction. In the hydrogen pressure atmosphere, pits and pores were observed on the surface of the 304 stainless steels. In addition, it was determined that Cl, an etchant component, was concentrated at a high concentration in the pits. SCC (stress corrosion cracking) was induced in the Cl atmosphere by stress caused by the abrasive embedded in the pits. It was assumed that the SCC mechanism is similar to HIC in that it occurs in the surface tensile stress and Cl atmosphere and is accompanied by grain boundary cracks similar to IGSCC (inter-granular SCC). The deformation induced phase transformation accompanied by planar slip should be related to the main cause of HIC in the hydrogen pressured atmosphere. Abnormal forbidden spots between the main diffraction spots were induced by the HIC in the hydrogen attacked area, where the microstructure was hardened. Understanding the HIC mechanism related to chloride corrosion can be used to assess the fitness of austenitic stainless steels for uses where there is a possibility of various susceptible cracking in hydrogen and chloride atmospheres.

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Jackson, E. M. L. E. M., P. E. de Visser e L. A. Cornish. "Distinguishing between Chi and Sigma phases in duplex stainless steels using potentiostatic etching". Materials Characterization 31, n. 4 (dicembre 1993): 185–90. http://dx.doi.org/10.1016/1044-5803(93)90061-y.

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Potgieter, J. H., L. M. Matthews e P. De Visser. "Experimental study of quantitative phase characterization in duplex stainless steels by potentiostatic etching". Journal of Materials Science 27, n. 13 (luglio 1992): 3667–79. http://dx.doi.org/10.1007/bf01151849.

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Lacasse, Robert, Christophe Hitz, Pierre-Antony Deschênes, Isabelle Montplaisir, Lydia Damphousse, Alexandre Lapointe, Carlo Baillargeon, Lindsay Grandy e Janine Mauzeroll. "Visualization and Location Determination of Pit Initiation Sites in Martensitic Stainless Steel during Corrosion-Fatigue Cyclic Plastic Deformation". ECS Meeting Abstracts MA2023-02, n. 14 (22 dicembre 2023): 1138. http://dx.doi.org/10.1149/ma2023-02141138mtgabs.

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Low-carbon martensitic stainless steels, such as 13%Cr4%Ni, are widely used in manufacturing hydraulic turbine runners. High tensile strength steel, such as cast CA6NM or wrought S41500 martensitic stainless steel, has an acceptable resistance to corrosion and cavitation, and reduces the weight and cost while offering a more efficient design. During operation, the combined effect of cyclic loading (fatigue) and corrosion reduces the fatigue strength and can initiate cracks at localized corrosion surface defects. In this study, we determined the bulk and localized corrosion behavior of wrought (S41500) and cast (CA6NM) 13%Cr4%Ni stainless steel before and after plastic deformation. Susceptibility to pitting corrosion was studied using open circuit potential and potentiodynamic polarization measurements in 0.020 M NaCl. Localized corrosion behavior was studied using a scanning droplet cell (SDC) and oil immersed scanning electrochemical cell microscopy (OI-SECCM). The bulk and localized electrochemical measurements after different surface preparation methods (mechanical polishing, followed by etching or electro-etching in different media) were compared. The surface defects including micro-voids and inclusions of different types were characterized. The location of pit initiation was then determined using scanning electron microscopy and profilometry imaging. A three-electrode microcell with a working electrode of 1 mm² was designed and hyphenated with optical microscope to allow in situ tracking of pit initiation and growth. Chronopotentiometry and chronoamperometry controlled pit initiation, while optical microscopy demonstrated dynamic release of corrosion products and measured oxide repassivation kinetics. Finally, the in situ technique was developed further to include a microtensiometer fatigue apparatus to study the synergy effect between corrosion and fatigue. Location of pit initiation was compared with and without plastic deformation. Videos of pit initiation and growth will be presented.

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Li, Yutang, Haoran Zhu, Dengping Ji, Bin Luo e Jianxun Fu. "Investigation on carbide dispersion modified by magnesium and rare earth in high-carbon martensitic stainless steel". Metallurgical Research & Technology 120, n. 5 (2023): 510. http://dx.doi.org/10.1051/metal/2023068.

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Fine and uniform carbides play a beneficial role in the high hardness and wear resistance of martensitic stainless steel. This paper investigates the effect of magnesium and rare earth(RE) on the dispersion of carbides in a high-carbon martensitic stainless steel. The results show that RE-Al-O and RE-Al-O-S inclusions were generated in RE-containing steel, while Mg-Al-O+(Ca, Mn)S and MgO+CaS inclusions were in Mg-containing steel. MC, M7C3, and M23C6 types of carbides were detected in both RE-containing and Mg-containing steels, which is consistent with thermodynamic calculation. The RE-Al-O inclusion can act as heterogeneous nuclei for carbides, while Mg-containing inclusions do not promote carbide precipitation for sulfur enrichment. The three-dimensional etching test suggests that RE-containing steel has more serious network carbides and larger carbide sizes than Mg-containing steel. The carbon segregation ratio presents an “M” shape due to δ→γ phase transformation. Rare earth is easy to combine with S and weaken the inhibiting effect of carbon segregation. Thus, magnesium has a stronger inhibitory effect on carbon segregation than rare earth.

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Juuti, Timo, Sampo Uusikallio, Antti J. Kaijalainen, Esa Heinonen, Nyo Tun Tun e David A. Porter. "The Effect of Sample Preparation on the Microstructure of Austenitic-Ferritic Stainless Steel". Materials Science Forum 879 (novembre 2016): 873–78. http://dx.doi.org/10.4028/www.scientific.net/msf.879.873.

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Sample preparation of metastable austenitic-ferritic steels can have a significant effect on the apparent microstructure due to the transformation of austenite to martensite (γ - α'). As a result, these steels often have a complex microstructure with ferrite and martensite, which have relatively similar crystal structures, making it very difficult to analyse. However, the quantitative analysis of such microstructures and the effect of the sample preparation are very important for the further study of the steel. In this research, the effect of sample preparation in metastable austenitic-ferritic stainless steel was studied by using three different sample preparation methods. In addition to conventional mechanical etching with colloidical silica and electropolishing, focused ion beam (FIB) milling was used to create an optimal sample surface to be further analysed with electron backscatter diffraction (EBSD). Micrographs were obtained from each sample before and after sample preparation using field emission scanning electron microscopy (FESEM) and laser scanning confocal microscopy (LSCM), and the microstructure was analysed using EBSD. The surface flatness required for good EBSD analysis was significantly better using FIB milling than mechanical polishing, while electropolishing results in the greatest topography and an arched sample surface. The amount of martensite was found to be dependent on the sample preparation: least martensite was formed during electropolishing, while surprisingly mechanical polishing and FIB milling resulted in equal amounts of martensite.

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Janis, Diana, Ryo Inoue, Andrey Karasev e Pär G. Jönsson. "Application of Different Extraction Methods for Investigation of Nonmetallic Inclusions and Clusters in Steels and Alloys". Advances in Materials Science and Engineering 2014 (2014): 1–7. http://dx.doi.org/10.1155/2014/210486.

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The characterization of nonmetallic inclusions is of importance for the production of clean steel in order to improve the mechanical properties. In this respect, a three-dimensional (3D) investigation is considered to be useful for an accurate evaluation of size, number, morphology of inclusions, and elementary distribution in each inclusion particle. In this study, the application of various extraction methods (chemical extraction/etching by acid or halogen-alcohol solutions, electrolysis, sputtering with glow discharge, and so on) for 3D estimation of nonmetallic Al2O3inclusions and clusters in high-alloyed steels was examined and discussed using an Fe-10 mass% Ni alloy and an 18/8 stainless steel deoxidized with Al. Advantages and limitations of different extraction methods for 3D investigations of inclusions and clusters were discussed in comparison to conventional two-dimensional (2D) observations on a polished cross section of metal samples.

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Zhang, Qinglian, Rongguang Wang, Masahiko Kato e Keijiro Nakasa. "Formation of Conical Carbides on the Surface of Stainless and Alloy Steels by Sputter-Etching". Journal of the Japan Institute of Metals 69, n. 3 (2005): 312–19. http://dx.doi.org/10.2320/jinstmet.69.312.

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NAKASA, Keijiro, Akihiro YAMAMOTO e Tsunetaka SUMOMOGI. "Gripping and frictional-conveying characteristics of fine protrusions formed by sputter-etching of stainless steels". Transactions of the JSME (in Japanese) 84, n. 862 (2018): 17–00360. http://dx.doi.org/10.1299/transjsme.17-00360.

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Yang, Ta-I., Yi-Chun Chen, Huei-Ting Huang, I.-Hsiang Tseng e Hsu-Wei Fang. "A STRATEGY TO ENHANCE THE BIOMEDICAL ARTICULATION SYSTEM BY ELECTROCHEMICALLY TEXTURING OF METAL SURFACES". Biomedical Engineering: Applications, Basis and Communications 24, n. 04 (agosto 2012): 343–47. http://dx.doi.org/10.4015/s1016237212500299.

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The concept of texturing steel surfaces were attempted to ease the surface wear and to prevent the release of harmful ions in the conventional joint replacement systems. The surfaces of the bio-compatible steels were textured by photolithography and electrochemical etching techniques to lower the friction coefficient and hence reduce the wear of the surface. Experimental results confirmed that the surfaces with textures (grooves) showed lower friction coefficient compared to un-textured surfaces at a high load (50 N). The friction coefficient could be further reduced for a lower load (10 N) through optimizing the generated hydrodynamic lift. A significant 47% reduction of friction coefficient was archived by tailoring the orientation and size of the textures on the stainless steel surface. The demonstrated strategy in this study would thus offer exciting avenues for developing artificial joint systems that last the full duration of the patients' life without any side-effect concerns.

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Varbai, Balázs, Timothy Pickle e Kornél Májlinger. "Development and Comparison of Quantitative Phase Analysis for Duplex Stainless Steel Weld". Periodica Polytechnica Mechanical Engineering 62, n. 3 (17 maggio 2018): 247–53. http://dx.doi.org/10.3311/ppme.12234.

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In duplex stainless steels the ideally 1:1 ratio of austenite-to-ferrite phases ensures the outstanding mechanical and corrosion properties compared to other, conventional stainless steel grades. However, this phase balance can be easily shifted to a mostly austenitic or mostly ferritic microstructures, depending on the welding process and heat input. In order to determine the phase ratio, several methods are available to use, such as Feritscope measurements, ASTM E562 manual point count method (on metallographic images) or quantitative image analysis. From these methods, Feritscope measurements cannot be applied to determine phase quantification in the narrow heat affected zone of duplex stainless steel welds – because of the very limited heat input. The manual point count method is very dependent of the assessor and cannot be automated. In this paper a histogram-based image analyzing process was developed, using Beraha's etchant solution. The results were compared to Feritscope measurements and a very good correlation (R2 = 0.9995) was found. This method will give the ability to easily and automatically measure phase ratio in weld metal, heat affected zone or in subsurface regions of multi-pass welds.

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NISHIMURA, Taiki, Hiroshi ABE e Yutaka WATANABE. "Detection and quantification of pre-existing plastic strain in austenitic stainless steels by potentiostatic etching method". Proceedings of the Materials and Mechanics Conference 2018 (2018): OS1213. http://dx.doi.org/10.1299/jsmemm.2018.os1213.

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Wang, E. Y., J. T. Cherian, A. Madsen e R. M. Fisher. "EELS characterization of “Smut” layer films on steel surface prepared for chrome plating by anodic etching". Proceedings, annual meeting, Electron Microscopy Society of America 53 (13 agosto 1995): 538–39. http://dx.doi.org/10.1017/s0424820100139068.

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Many steel parts are electro-plated with chromium to protect them against corrosion and to improve their wear-resistance. Good adhesion of the chrome plate to the steel surface, which is essential for long term durability of the part, is extremely dependent on surface preparation prior to plating. Recently, McDonnell Douglas developed a new pre-treatment method for chrome plating in which the steel is anodically etched in a sulfuric acid and hydrofluoric acid solution. On carbon steel surfaces, this anodic pre-treatment produces a dark, loosely adhering material that is commonly called the “smut” layer. On stainless steels and nickel alloys, the surface is only darkened by the anodic pre-treatment and little residue is produced. Anodic pre-treatment prior to hard chrome plating results in much better adherence to both carbon and alloy steels.We have characterized the anodic pre-treated steel surface and the resulting “smut” layer using various techniques including electron spectroscopy for chemical analysis (ESCA) on bulk samples and transmission electron microscopy (TEM) and electron energy-loss spectroscopy (EELS) on stripped films.

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Abe, Seizaburo, e Akihiko Takahashi. "Material Factors of Grain Boundary Sensitization in Stainless Steels Detected by 10% Oxalic Acid Etching Test Method". Zairyo-to-Kankyo 49, n. 6 (2000): 374–78. http://dx.doi.org/10.3323/jcorr1991.49.374.

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TAKIZAWA, Kikuo, e Yoshinori NAKAYAMA. "Effects of MnS Inclusion and the Potentiostatic Etching Treatment on Pitting Corrosion Resistance of 18-8 Stainless Steels." Journal of the Surface Finishing Society of Japan 42, n. 6 (1991): 649–54. http://dx.doi.org/10.4139/sfj.42.649.

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Nakamura, Masayoshi, Keijiro Nakasa, Yudai Kitamika, Sande Gao e Tsunetaka Sumomogi. "Formation of Fine Protrusions by Sputter Etching of Stainless Steels and Evaluation of Gripping Ability of Fiber Sheets". International Journal of Precision Engineering and Manufacturing 22, n. 4 (5 marzo 2021): 689–96. http://dx.doi.org/10.1007/s12541-021-00495-0.

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Terek, Vladimir, Aleksandar Miletić, Lazar Kovačević, Dragan Kukuruzović, Branko Škorić, Peter Panjan e Pal Terek. "Surface Topography and Grain Morphology of Nanolayer TiAlN/TiSIN Coating Governed by Substrate Material and Rotation during Deposition". Materials Proceedings 2, n. 1 (12 maggio 2020): 32. http://dx.doi.org/10.3390/ciwc2020-06822.

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Nanolayer TiAlN/TiSiN coating is one of the most advanced contemporary protective coatings. It has been applied for protection of machining tools, forming tools, and die casting tools. However, due to its versatile properties, there is a high potential for broadening its application; for example, for protection of biomedical implants. Each application requires specific base materials, for example cold working steels are used for forming, while stainless steels are applied for biomedical purposes. Different materials and their pre-treatment might result in different coating properties even if coating was conducted in a single batch. Real tools and components have complex geometries, and as such require a multiple-axis rotation during the deposition. Among other properties, grain morphology and surface topography are of great importance in a real application. Since systematic studies on the effect of substrate materials and rotation during deposition on these properties are very scarce, in this article we studied TiAlN/TiSiN coating magnetron sputtered on five different substrates, prepared with 1-, 2-, and 3-fold rotations. Cold-work tool steel (X153CrMoV12), hot-work tool steel (X37CrMoV5-1), plasma-nitrided hot-work tool steel, surgical stainless steel (X2CrNiMo18-15-3), and cemented carbide (WC/Co) were used as substrate materials. Three-dimensional stylus profilometry and atomic force microscopy were used for evaluation of micro and nano topography. The coated surgical steel has the highest roughness (Sa) which corresponds to the highest number of coating growth defects. However, the size of the individual growth defects was considerably smaller for this substrate than for other substrate materials. The observed difference is linked to differences in the concentration of specific carbides contained in a specific steel. Since different carbides have different polishing and ion-etching rates, coatings on different steels may have different concertation of defects. Columnar grain analysis revealed that coating on surgical steel exhibited the smallest column diameter (125 nm) and their highest uniformity. Column diameter on other substrates is around 215 nm, while hot-working tool steel exhibited the largest columns (235 nm). Such findings suggest that the same coating may exhibit different mechanical properties on different substrates. Coatings produced with the higher degree of rotation (2-fold, 3-fold) have fewer defects and a smoother surface. There was no clear trend between columnar grain size and the number of rotational degrees.

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NAKASA, Keijiro, Akihiro YAMAMOTO, Rongguang WANG e Tsunetaka SUMOMOGI. "Effect of plasma nitriding on the compressive strength of multi-functional fine protrusions formed by sputter-etching of stainless steels". Transactions of the JSME (in Japanese) 82, n. 838 (2016): 16–00059. http://dx.doi.org/10.1299/transjsme.16-00059.

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Smolentsev, V. P., A. V. Levin e A. V. Gribentchikov. "Manufacturing of Coated Production Tooling". Advanced Materials Research 24-25 (settembre 2007): 13–16. http://dx.doi.org/10.4028/www.scientific.net/amr.24-25.13.

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It is difficult to select the materials combining in modern industry, this paper analyzed the drawbacks of different materials (the stainless, the copper alloys, aluminum and its alloys) on selecting materials for tooling and selection of coatings that help to eliminate drawbacks, analyzed the micro-arc oxidation (MAO) and its application of different materials. It is ascertained that aluminum alloys may be practical to use for electrodes for electroerosive machining only in exceptional cases when the wear of the tool is not determinative. Selection of materials combining required physical and mechanical properties may be a difficult task in tooling designing and manufacturing in modern industry. This problem is especially evident when current-conducting elements of tooling used for electrophysical and electrochemical processing methods are manufactured. The main distinctive feature of these methods is maintenance of values under the influence of electrical current and corrosive medium and during electrochemical reactions. The article addresses comparative analysis of properties of different materials used for tooling manufacture, advantages and drawbacks of these materials and selection of coatings that help to eliminate drawbacks. When selecting materials for tooling, the alloy in use shall have the following properties [4]: high electrical conductivity, high corrosion resistance, high resistance to local fracture, high adhesion to dielectric coatings, sufficient mechanical strength, high machinability and low cost. The following materials are considered to meet operating requirements to the fullest extend [4.5]: stainless steels and copper alloys that have high machinability, electrical conductivity, weldability and mechanical strength; titanium- and chromium-base alloys that have high mechanical strength, corrosion resistance and resistance to local fracture and enables to make oxide insulating layer protecting surface from anodic dissolution. However, these materials have a number of drawbacks, the most important of which is high cost that impedes their usage especially in serial production. Furthermore, stainless steels and titaniumand chromium-base alloys have the following drawbacks that affect product cost: - complexity of machinability that results in high labor-intensiveness of manufacturing process of tooling; - heavy losses in electric voltage provided that these materials are used as current-carrying elements that makes current supply calculation difficult and requires application of more powerful sources; - cracking and fracture of oxide surface coating even when mechanical effect is insignificant that results in loss of isolating and protective properties [1,2]. Furthermore, oxide coating application process cannot be controlled completely and as a result, coating uniformity in thickness, composition and properties cannot be achieved. Application of coatings to the areas with varied sections and to the surfaces with projections and sharp edges is a difficult problem. Layers applied to these surfaces have little adhesion to parent material and their thickness is limited due to high stress concentration and etching. The revealed drawbacks require development and usage of surface layer improvement process to receive required physical and mechanical properties of composite material.

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VOLCHUK, V. M., V. I. KACHUR e I. A. TIUTIERIEV. "RESEARCH OF PRODUCTION TECHNOLOGY AND PROPERTIES OF THE BLADE IS MADE BY THE MINE WELDING METHOD". Physical Metallurgy and Heat Treatment of Metals, n. 2 (101) (21 ottobre 2023): 7–19. http://dx.doi.org/10.30838/j.pmhtm.2413.040723.7.979.

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Problem statement. One of the main requirements for the blade is to achieve significant indicators of corrosion resistance and elasticity, the ability to withstand lateral and contact loads. Thanks to the combination of high-carbon and stainless steels with the help of pit welding, the effect of zone hardening is achieved in the subsequent heat treatment. Zone hardening technology is a combination of different hardness indicators on one knife blade, which leads to a significant increase in the elasticity and durability of the blade, reduces the risk of hardening cracks. Mine welding allows you to combine into a composite steels that have a high content of carbon (С = 0,9…1 %, С = 0,4…0,45 %) and chromium (Cr = 13…14 %), which with an ordinary electric arc method is practically impossible to do. High carbon equivalent and chromium doping complicates existing welding processes. With the appropriate modes of thermoplastic deformation, we get in the zone of forge welding a monolithic connection of two steels at the atomic level, which in itself is already a composite (combination of two materials with different properties to obtain a third starting material). Materials and methods. Etching the blade in an acid solution. To obtain blanks for blacksmithing (pit welding), we took steel bar ШХ15Ш (ТУ141594 DSTU4738:007) Ø – 20 mm, length L − 80 mm for the cutting part of the blade, steel bar 40Х13 DSTU 7838:007, for covers Ø − 20 mm, L − 150 mm. The total weight of the package is 0,42 kg. The results of the experiment. When conducting four experimental attempts to determine the tempering temperature-time regimes for a composite knife blade (ШХ15Ш in 40Х13 facings), the following parameters were obtained: 1. heating temperature 260…270 °С; 2. exposure for 1,8…2 hours; 3. cooling − air. The hardness of the blade is 58−59 HRC, the cutting part is 52−54 HRC of the coating. With such indicators, the maximum indicators of wear resistance of the cutting edge and high indicators of blade elasticity were obtained. For steel n690: 1. heating temperature for tempering 200…220 °С; 2. exposure for 1 hour; 3. cooling − air. Conclusions. Knife blades are proposed to be made by manual forging, without the use of pneumatic and hydraulic hammers, to ensure the purity of the experiment. The work includes calculations of heat treatment regimes, analysis of the microstructures of the obtained monosteel and composite, economic feasibility, advantages and disadvantages of one method of obtaining a blade blade over another.

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F., Dias, D., M. G. Diniz e Pimenta, A. R. "Propriedades mecânicas das fases ferrita e austenita de aço inoxidável duplex". STUDIES IN ENGINEERING AND EXACT SCIENCES 2, n. 1 (21 settembre 2021). http://dx.doi.org/10.54018/seesv2n1-001.

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Aços inoxidáveis duplex apresentam elevada resistência mecânica e resistência à corrosão, propriedades requeridas pelas indústrias petroquímicas. Esta combinação tem ampliado a utilização destes aços, e motivado diversas pesquisas. Os aços inoxidáveis duplex recebem este nome, devido à microestrutura ser formada por aproximadamente 50% de austenita e 50% de ferrita. Sabe-se que a dureza está diretamente relacionada à resistência mecânica, e que esta propriedade pode variar de acordo com a microestrutura do material. O objetivo do presente trabalho é avaliar e comparar a dureza das fases austenita e ferrita presentes nos aços duplex. Uma amostra foi preparada metalográficamente, sendo posteriormente atacada com a solução Behara pela técnica de “color etching”. Após o ataque químico as amostras foram submetidas a ensaios de microdureza Vickers, apresentando 247,8±35,1 HV0,1 e 263,22±11,6 HV0,1 para a ferrita e austenita, respectivamente. Após analise estatística dos resultados, concluiu-se que as fases ferrita e austenita possuem durezas similares. Duplex stainless steels have high mechanical strength and corrosion resistance properties required by the petrochemical industry. This combination has expanded the use of these steels, and motivated many studies. The duplex stainless steels are named because of the microstructure is formed by about 50% to 50% austenite and ferrite. It is known that the hardness is directly related to mechanical strength, and that this property can vary depending on the microstructure of the material. The objective of this study is to evaluate and compare the hardness of austenite and ferrite phases present in the duplex stainless steels. A sample was prepared by metallographic preparation techniques, and was then attacked with the solution BEHARA with technique of color etching. After etching the samples were tested for Vickers microhardness, with 247.8 ± 35.1 HV0, 1 and 263.22 ± 11.6 HV0, 1 for ferrite and austenite, respectively. After statistical analysis of results showed that the ferrite and austenite phases have similar hardness.

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Řehořek, Jakub, e Hygreeva Kiran Namburi. "Basic Microstructural Characterization of Second Phases in Homogeneous Weld Joint Made of X6CrNiNbN25-20 Steel After Long-Term Exposure Time at 973 K". Journal of Nuclear Engineering and Radiation Science 7, n. 2 (16 novembre 2020). http://dx.doi.org/10.1115/1.4048900.

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Abstract New blocks of fossil fuel power plants designed for steam temperatures above 873 K require advanced stainless steels as material for superheater or reheater systems. Weld joints are critical parts in fossil power units. Great attention is paid to the exploitation of new steel grades with higher material properties. In the austenitic steels family, the superior grade is undoubtedly HR3C steel (X6CrNiNbN25-20). A detailed knowledge on stability and microstructure composition during thermal exposure of the weld joints made from HR3C is necessary in order to use them in fossil fuel power plants with ultrasupercritical (USC) and new advanced ultrasupercritical (A-USC) steam parameters. The aim of the paper is to identify critical minor phases in HR3C steel, which allow acceleration of creep damage. The σ-phase and rough carbides M23C6 type is considered as such a phases in this steel. In this study, the σ-phase is identified and studied in more detail in relation to the development of creep damage at 973 K. Experimental material of the homogeneous HR3C weld joints in two states: in the as-welded state (AW) and after the postweld heat treatment (PWHT). Weld joints were manufactured by orbital welding using the gas tungsten arc welding (GTAW) method, heat input Qs = 1600 J/mm, interpass 423 K, three beads. Nickel-base alloy UTP A6170 Co (equivalent to Thermanit 617) was used as a filler material. The PWHT was carried out at the temperature of 1503 K for 15 min. Stress rupture tests were performed on the cross-weld (CW) joints of tubes ø 38 × 6.3 mm at 973 K with times to rupture up to nearly 22,000 h. The polished surface of the longitudinal sections was subjected to color etching in Murakami (30 g K3(Fe(CN)6), 30 g KOH, 60 ml H2O) in order to highlight the σ-phase. Several microscopic techniques were used for the study. The results were supplemented by creep, grain size, and microhardness data hardness vickers (HV) 0.5. The PWHT specimens exhibited an average σ-phase size of approximately 5 μm as well as AW specimens in specimens with short time to rupture (tr). However, tr such as 20,000 h, the average σ-phase size already reached dangerous border 10 μm. The AW specimens as opposed to the PWHT specimens did not show a noticeable growth of austenitic grains in the heat-affected zone (HAZ). In specimens after PWHT, the average grain size in HAZ was more than twice that of the body material (BM). It is worth noting that creep ductility values of specimens in the state after PWHT are very low, which is the result of coarse-grained structure in the HAZ and accelerated precipitation of σ-phase particles along grain boundaries during creep at 973 K.

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