Academic literature on the topic 'S-phase, stainless steel, nitriding, carburising'
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Journal articles on the topic "S-phase, stainless steel, nitriding, carburising"
1
Karadas, Riza, Ozgur Celik, and Huseyin Cimenoglu. "Low Temperature Nitriding of a Martensitic Stainless Steel." Defect and Diffusion Forum 312-315 (April 2011): 994–99. http://dx.doi.org/10.4028/www.scientific.net/ddf.312-315.994.
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Nitriding is as an effective technique applied for many years to improve the surface hardness and wear resistance of low carbon and tool steels [1]. In the case of stainless steels, increase of surface hardness and wear resistance accompany by a drop in corrosion resistance due to the precipitation of CrN. In this respect, many attempts have been made to modify the surfaces of austenitic stainless steels to increase their surface hardness and wear resistance without scarifying the corrosion resistance [2-6]. It is finally concluded that, nitriding at temperatures lower than conventional nitriding process (which is generally about 550°C) has potentiality to produce a nitrogen expanded austenite (also known as S-phase), on the surface without formation of CrN. Due to the superb properties of the S-phase, the low temperature nitrided austenitic stainless steels exhibit very high surface hardness, a good wear resistance, and more importantly, an excellent corrosion resistance. Recently some attempts have been made to apply low temperature nitriding to martensitic stainless steels, which are widely used in the industries of medicine, food, mold and other civil areas [7-9]. In these works, where nitriding has been conducted by plasma processes, superior surface hardness, along with excellent wear and corrosion resistances have been reported for AISI 410 and AISI 420 grade martensitic stainless steels. This work focuses on low temperature gas nitriding of AISI 420 grade martensitic stainless steel in a fluidized bed reactor. In this respect the microstructures, phase compositions, hardness, wear and corrosion behaviours of the original and nitrided martensitic stainless steels have been compared.
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Nishimoto, Akio, and Katsuya Akamatsu. "Effect of Pre-Deforming on Plasma Nitriding Response of 304 Stainless Steel." Materials Science Forum 654-656 (June 2010): 1811–14. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.1811.
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The effect of a modified layer caused by pre-deforming on the low temperature plasma nitriding of AISI 304 austenitic stainless steel was investigated. The aim of using the deformed layer is to produce a thicker nitrided layer and to decrease the nitriding temperature due to the much faster diffusion of nitrogen. The pre-deformed sample was prepared by the rolling in 0, 1, 2, 3, and 4% ratios. Plasma nitriding was carried out at 673 and 723 K for 18 ks under 600 Pa pressures in presence of N2/H2 in 50:50 ratio. The microhardness, thickness and phase composition of nitrided layers formed on the surface of pre-deformed and non-deformed samples were investigated using Vickers microhardness tester, optical microscope and X-ray diffraction techniques, respectively. After nitriding, maximum hardness ~1150 HV was achieved on the pre-deformed sample. XRD pattern showed that most dominant phase of the nitrided layer consisted of the expanded austenite (S phase). In addition, the pre-deforming by rolling had a significant influence on the hardness and thickness of the S phase. That is, the hardness and thickness of the S phase were increased by applying the pre-deformation.
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Haruman, E., Y. Sun, H. Malik, Agus Geter E. Sutjipto, S. Mridha, and K. Widi. "Low Temperature Fluidized Bed Nitriding of Austenitic Stainless Steel." Solid State Phenomena 118 (December 2006): 125–30. http://dx.doi.org/10.4028/www.scientific.net/ssp.118.125.
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In the present investigation, low temperature nitriding has been attempted on AISI 316L austenitic stainless steel by using a laboratory fluidized bed furnace. The nitriding was performed in temperature range between 400°C and 500°C. X-ray diffraction, metallography, and corrosion tests were used to characterize the resultant nitrided surface and layers. The results showed that fluidized bed process can be used to produce a precipitation-free nitrided layer characterized by the S phase or expanded austenite on austenitic stainless steel at temperatures below 500°C. But there exists a critical temperature and an incubation time for effective nitriding, below which nitriding is ineffective. The corrosion behaviour of the as-nitrided surfaces is significantly different from that previously reported for low temperature plasma nitriding. This anomaly is explained by the formation of iron oxide products and surface contamination during the fluidized process.
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Adachi, Shinichiro, Motoo Egawa, Takuto Yamaguchi, and Nobuhiro Ueda. "Low-Temperature Plasma Nitriding for Austenitic Stainless Steel Layers with Various Nickel Contents Fabricated via Direct Laser Metal Deposition." Coatings 10, no. 4 (April 7, 2020): 365. http://dx.doi.org/10.3390/coatings10040365.
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In this study, low-temperature plasma nitriding is applied to austenitic stainless steels at temperatures below 450 °C. This enhances the wear resistance of the steels with maintaining corrosion resistance, by producing expanded austenite (known as the S-phase), which dissolves excessive nitrogen. Austenitic stainless steels contain nickel, which has the potential to play an important role in the formation and properties of the S-phase. In this experiment, austenitic stainless steel layers with different nickel contents were processed using direct laser metal deposition, and subsequently treated using low-temperature plasma nitriding. As a result, the stainless steel layers with high nickel contents formed the S-phase, similar to the AISI 316L stainless steel. The thickness and Vickers hardness of the S-phase layers varied with respect to the nickel contents. Due to lesser chromium atoms binding to nitrogen, the chromium content relatively decreased. Moreover, there was no evident change in the wear and corrosion resistances due to the nickel contents.
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GHELLOUDJ, Elhadj. "MICROSTRUCTURE, MECHANICAL AND TRIBOLOGICAL BEHAVIOUR OF AISI 316L STAINLESS STEEL DURING SALT BATH NITRIDING." Acta Metallurgica Slovaca 27, no. 2 (June 1, 2021): 47–52. http://dx.doi.org/10.36547/ams.27.2.952.
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The aim of the current work was to analyse the impact of salt bath nitriding on the behavior of the tribological characteristics and surface microstructures of AISI 316L stainless steels. Nitriding was carried out at 580°C for 10 h. The tribological, structural behavior of the AISI 316L before and after salt bath nitriding was compared. The surface microstructures, tribological characteristics, as well as its surface hardness, were investigated using optical microscopy (OM), X-ray diffractometer (XRD), surface profilometer, pin-on-disk wear tester and microhardness tester. In the current work the experimental results showed that a great surface hardness could be achievable through salt bath nitriding technique because of the formation of the so-called expanded Austenite (S-phase), the nitrogen diffusion region. The surface hardness of AISI 316 stainless steel after nitriding process reached 1100 HV0.025 which was six times the untreated sample hardness. The S-phase is additionally expected to the improvement of wear resistance and decrease the friction coefficient.
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Adachi, Shinichiro, Takuto Yamaguchi, and Nobuhiro Ueda. "Formation and Properties of Nitrocarburizing S-Phase on AISI 316L Stainless Steel-Based WC Composite Layers by Low-Temperature Plasma Nitriding." Metals 11, no. 10 (September 27, 2021): 1538. http://dx.doi.org/10.3390/met11101538.
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Stainless steel-based WC composite layers fabricated by a laser cladding technique, have strong mechanical strength. However, the wear resistance of WC composite layers is not sufficient for use in severe friction and wear environments, and the corrosion resistance is significantly reduced by the formation of secondary carbides. Low-temperature plasma nitriding and carburizing of austenitic stainless steels, treated at temperatures of less than 450 °C, can produce a supersaturated solid solution of nitrogen or carbon, known as the S-phase. The combined treatment of nitriding and carburizing can form a nitrocarburizing S-phase, which is characterized by a thick layer and superior cross-sectional hardness distribution. During the laser cladding process, free carbon was produced by the decomposition of WC particles. To achieve excellent wear and corrosion resistance, we attempted to use this free carbon to form a nitrocarburizing S-phase on AISI 316 L stainless steel-based WC composite layers by plasma nitriding alone. As a result, the thick nitrocarburizing S-phase was formed. The Vickers hardness of the S-phase ranged from 1200 to 1400 HV, and the hardness depth distribution became smoother. The corrosion resistance was also improved through increasing the pitting resistance equivalent numbers due to the nitrogen that dissolved in the AISI 316 L steel matrix.
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Adachi, Shinichiro, and Nobuhiro Ueda. "Wear and Corrosion Properties of Cold-Sprayed AISI 316L Coatings Treated by Combined Plasma Carburizing and Nitriding at Low Temperature." Coatings 8, no. 12 (December 10, 2018): 456. http://dx.doi.org/10.3390/coatings8120456.
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Cold-sprayed AISI 316L stainless steel coatings are treated to form an austenite phase with excessive dissolved nitrogen (known as the S-phase) by plasma nitriding at temperatures below 450 °C. The S-phase is a hard and wear-resistant layer with high corrosion resistance. However, the S-phase layer formed after only nitriding is thin and the hardness abruptly decreases at a certain depth; it lacks mechanical reliability. We examined two types of combined low-temperature plasma treatment to enhance the mechanical reliability of the S-phase layer: (i) sequential and (ii) simultaneous. In the sequential plasma treatment, the carburizing step was followed by nitriding. In the simultaneous treatment, the nitriding and carburizing steps were conducted at the same time. Both combined plasma treatments succeeded in thickening the S-phase layers and changed the hardness depth profiles to decrease smoothly. In addition, anodic polarization measurements indicated that sequential treatment involving carburizing followed by nitriding for 2 h each resulted in high corrosion resistance.
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Sumiya, Kenzo, Shinkichi Tokuyama, Akio Nishimoto, Junichi Fukui, and Atsushi Nishiyama. "Application of Active-Screen Plasma Nitriding to an Austenitic Stainless Steel Small-Diameter Thin Pipe." Metals 11, no. 2 (February 22, 2021): 366. http://dx.doi.org/10.3390/met11020366.
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Low-temperature active-screen plasma nitriding (ASPN) was applied in this study to improve the bending rigidity and corrosion resistance of a small-diameter thin pipe composed of austenitic stainless steel (SUS 304). The inner and outer diameters of the pipe were ϕ0.3 and ϕ0.4 mm, respectively, and the pipe length was 50 mm. The jig temperature was measured using a thermocouple and was adopted as the nitriding temperature because measuring the temperature of a small-diameter pipe is difficult. The nitriding temperature was varied from 578 to 638 K to investigate the effect of temperature on the nitriding layer and mechanical property. The nitriding layer thickness increased with an increase in nitriding temperature, reaching 15 μm at 638 K. The existence of expanded austenite (S phase) in this nitriding layer was revealed using the X-ray diffraction pattern. Moreover, the surface hardness increased with the nitriding temperature and took a maximum value of 1100 HV above 598 K. The bending load increased with an increase in the nitriding temperature in relation to the thicker nitriding layer and increased surface hardness. The nitrided samples did not corrode near the center, and corrosion was noted only near the tip at high nitriding temperatures of 618 and 638 K in a salt spray test. These results indicated that the bending rigidity of the small-diameter thin pipe composed of austenitic stainless steel was successfully improved using low-temperature ASPN while ensuring corrosion resistance.
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Gołębiowski, Bartosz, and Wiesław Świątnicki. "Microstructural Changes Induced during Hydrogen Charging Process in Stainless Steels with and without Nitrided Layers." Solid State Phenomena 186 (March 2012): 305–10. http://dx.doi.org/10.4028/www.scientific.net/ssp.186.305.
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The purpose of this study is to analyze the effect of glow discharge nitriding on hydrogen degradation of two types of steels: two-phase austenitic-ferritic and single-phase austenitic. The nitriding process resulted in formation of surface layers composed of expanded austenite (S phase), and in the case of two-phase steel of expanded austenite and expanded ferrite. Microstructural changes occurring under the influence of hydrogen on steels without and with nitrided layers were investigated with the use of scanning (SEM) and transmission (TEM) electron microscopy techniques. It was shown that the density of cracks formed during cathodic hydrogen charging is higher on the surface of the non-nitrided steels compared to the nitrided steels after identical hydrogen charging process. Moreover in non nitrided steel hydrogenation leads to considerable increase of dislocation density, which results from the high concentration of hydrogen absorbed to the steel during its cathodic charging. This leads in turn to high stress concentration and local embrittlement giving rise to cracks formation. Conversely nitriding reduces the absorption of hydrogen and prevents structural changes resulting in hydrogen embrittlement. The conducted studies show that glow discharge nitriding can be used to increase resistance to hydrogen embrittlement of austenitic and austenitic ferritic stainless steels.
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GAO, YUXIN, and SHAOMEI ZHENG. "EFFECT OF PLASMA NITRIDING TEMPERATURES ON CHARACTERISTICS OF AISI 201 AUSTENITIC STAINLESS STEEL." Surface Review and Letters 23, no. 01 (February 2016): 1550084. http://dx.doi.org/10.1142/s0218625x15500845.
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Samples of AISI 201 austenitic stainless steel were produced by plasma nitriding at 350[Formula: see text]C, 390[Formula: see text]C, 420[Formula: see text]C, 450[Formula: see text]C and 480[Formula: see text]C for 5[Formula: see text]h. Systematic characterization of the nitrided layer was carried out in terms of micrograph observations, phase identification, chemical composition depth profiling, surface microhardness measurements and electrochemical corrosion tests. The results show that the surface hardness and the layer thickness increased with increasing temperature. XRD indicated that a single S-phase layer was formed during low temperature ([Formula: see text][Formula: see text]420[Formula: see text]C), while Cr2N or CrN phase was formed besides S-phase when nitrided at 450[Formula: see text]C and 480[Formula: see text]C. The specimen treated at 390[Formula: see text]C presents a much enhanced corrosion resistance compared to the untreated substrate. The corrosion resistance deteriorated for samples treated above 450[Formula: see text]C due to the formation of chromium nitrides.
Dissertations / Theses on the topic "S-phase, stainless steel, nitriding, carburising"
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Münter, Daniel. "Struktur und Korrosionsverhalten nichtrostender Stähle nach einer chemisch-thermischen Behandlung bei tiefen Temperaturen." Doctoral thesis, TU Bergakademie Freiberg, 2009. https://tubaf.qucosa.de/id/qucosa%3A22712.
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Rost- und säurebeständige Stähle, wie z.B. der Austenit 1.4404, zeichnen sich durch eine hervorragende Korrosionsbeständigkeit aus. Der Einsatz dieser Stähle war aber aufgrund ihrer schlechten Verschleißeigenschaften bisher eher eingeschränkt. Um diesen Anforderungen gerecht zu werden, ist es notwendig, eine Oberflächenmodifizierung vorzunehmen. Dies kann besonders mit Nitrier- und Carburierverfahren bzw. einer Kombination aus beiden erreicht werden, wobei das im Mischkristall gelöste Chrom nicht zur Ausscheidung als Chromnitrid bzw. Chromcarbid gebracht werden darf. Dazu wurde bereits Mitte der 80-er Jahre das Verfahren der so genannten Tieftemperaturnitrierung entwickelt. Mit Hilfe dieses Verfahrens ist es möglich, auf rost- und säurebeständigen Stählen eine Schicht mit hohem Verschleißwiderstand zu erzeugen, ohne dass es zum Verlust der Korrosionsbeständigkeit kommt.
Die werkstoffwissenschaftliche Forschung hat mit dieser überwiegend technologischen Entwicklung nicht Schritt gehalten. Verallgemeinerungsfähige Aussagen über das Korrosionsverhalten dieser verschleißbeständigen Randschichten in Abhängigkeit von ihrer Zusammensetzung und Struktur sind gegenwärtig noch nicht möglich. Die Zielstellung der im Rahmen dieser Arbeit durchzuführenden Untersuchungen besteht deshalb in der Ermittlung vertiefter Kenntnisse über den Zusammenhang zwischen den Behandlungsbedingungen, der Struktur und der chemischen Zusammensetzung der dabei entstehenden Randschichten und ihrem Korrosionsverhalten.
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Münter, Daniel. "Struktur und Korrosionsverhalten nichtrostender Stähle nach einer chemisch-thermischen Behandlung bei tiefen Temperaturen." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2010. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-27260.
Full textAbstract:
Rost- und säurebeständige Stähle, wie z.B. der Austenit 1.4404, zeichnen sich durch eine hervorragende Korrosionsbeständigkeit aus. Der Einsatz dieser Stähle war aber aufgrund ihrer schlechten Verschleißeigenschaften bisher eher eingeschränkt. Um diesen Anforderungen gerecht zu werden, ist es notwendig, eine Oberflächenmodifizierung vorzunehmen. Dies kann besonders mit Nitrier- und Carburierverfahren bzw. einer Kombination aus beiden erreicht werden, wobei das im Mischkristall gelöste Chrom nicht zur Ausscheidung als Chromnitrid bzw. Chromcarbid gebracht werden darf. Dazu wurde bereits Mitte der 80-er Jahre das Verfahren der so genannten Tieftemperaturnitrierung entwickelt. Mit Hilfe dieses Verfahrens ist es möglich, auf rost- und säurebeständigen Stählen eine Schicht mit hohem Verschleißwiderstand zu erzeugen, ohne dass es zum Verlust der Korrosionsbeständigkeit kommt.
Die werkstoffwissenschaftliche Forschung hat mit dieser überwiegend technologischen Entwicklung nicht Schritt gehalten. Verallgemeinerungsfähige Aussagen über das Korrosionsverhalten dieser verschleißbeständigen Randschichten in Abhängigkeit von ihrer Zusammensetzung und Struktur sind gegenwärtig noch nicht möglich. Die Zielstellung der im Rahmen dieser Arbeit durchzuführenden Untersuchungen besteht deshalb in der Ermittlung vertiefter Kenntnisse über den Zusammenhang zwischen den Behandlungsbedingungen, der Struktur und der chemischen Zusammensetzung der dabei entstehenden Randschichten und ihrem Korrosionsverhalten.
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Martinavičius, Andrius. "Structural and transport property changes in austenitic stainless steel induced by nitrogen incorporation." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-68719.
Full textAbstract:
The saturation of the near surface layers of metals with different elements is a powerful tool to change their surface properties. In this work, structure and transport changes induced by incorporation of large amounts of nitrogen at moderate temperatures (∼370−430°C) in austenitic stainless steel are investigated. The structural study of the plasma nitrided ASS has been carried out using a combination of global (X-ray diffraction, nuclear reaction analysis) and local probe techniques (Mossbauer, X-ray absorption near edge structure, extended X-ray absorption fine structure spectroscopies). It reveals that nitriding at moderate temperatures (∼400°C) results in the nitrided layer with Fe, Cr and Ni being in different local chemical environments: Cr in the CrN-like state, Fe in the Fe4N-like state, Ni in the metallic state. The results demonstrate that the incorporation of interstitial nitrogen destabilizes homogeneous distribution of the ASS constituents, which leads to the segregation of the elements into small zones rich in Cr and Ni and provide strong evidence that the decomposition is of a spinodal nature. These experimental findings contradict the widely accepted view that the phase formed during nitriding at moderate temperatures is a homogeneous supersaturated nitrogen solid solution.
The nitrogen atomic transport study has been carried out by using ion beam nitriding of single-crystalline stainless steel, and the issues of the influence of the crystalline orientation, nitriding temperature, ion flux and ion energy are addressed. The diffusion coefficients have been extracted from the fitting of the nitrogen depth profiles by using the trapping-detrapping model. It is shown that the crystalline orientation plays a significant role in nitrogen diffusion: the penetration depth is largest, intermediate and lowest for the (001), (110) and (111) orientation, respectively. The pre-exponential factor D0 varies by two orders of magnitude depending on the orientation, while the activation energy E is similar (∼1.1 eV) for the (111) and (110) orientations and higher for the (001) orientation (∼1.4 eV). It is found that the nitrogen ion energy and the flux have the effect on the nitrogen transport in the bulk with higher energies (or fluxes) showing larger diffusion coefficients. The ion energy effect is more pronounced for the (001) than for the (111) orientation, while the flux effect is similar in both orientations. In addition, the diffusivity during post-nitriding thermal annealing without ion irradiation is found to be independent of the crystalline orientation. The observed radiation enhanced diffusion and anisotropy are discussed on the basis of nitrogen incorporation induced changes in the matrix structure (ASS decomposition and formation heterogeneous structure), ion bombardment induced effects (defects, localized vibrations) and correlated diffusion.
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Dalton, John Christian. "Surface Hardening of Duplex Stainless Steel 2205." Case Western Reserve University School of Graduate Studies / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1480696856644048.
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Dalton, John Christian. "Thermodynamics of Paraequilibrium Carburization and Nitridation of Stainless Steels." Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1386586585.
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Kutschmann, Pia, Thomas Lindner, Kristian Börner, Ulrich Reese, and Thomas Lampke. "Effect of Adjusted Gas Nitriding Parameters on Microstructure and Wear Resistance of HVOF-Sprayed AISI 316L Coatings." MDPI AG, 2019. https://monarch.qucosa.de/id/qucosa%3A34775.
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Gas nitriding is known as a convenient process to improve the wear resistance of steel components. A precipitation-free hardening by low-temperature processes is established to retain the good corrosion resistance of stainless steel. In cases of thermal spray coatings, the interstitial solvation is achieved without an additional surface activation step. The open porosity permits the penetration of the donator media and leads to a structural diffusion. An inhomogeneous diffusion enrichment occurs at the single spray particle edges within the coating’s microstructure. A decreasing diffusion depth is found with increasing surface distance. The present study investigates an adjusted process management for low-temperature gas nitriding of high velocity oxy-fuel-sprayed AISI 316L coatings. To maintain a homogeneous diffusion depth within the coating, a pressure modulation during the process is studied. Additionally, the use of cracked gas as donator is examined. The process management is designed without an additional surface activation step. Regardless of surface distance, microstructural investigations reveal a homogeneous diffusion depth by a reduced processing time. The constant hardening depth allows a reliable prediction of the coatings’ properties. An enhanced hardness and improved wear resistance is found in comparison with the as-sprayed coating condition.
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Lindner, Thomas. "Verfahrenskombination zur Randschichthärtung thermisch gespritzter Schichtsysteme aus austenitischem Stahl." Eigenverlag, 2018. https://monarch.qucosa.de/id/qucosa%3A31358.
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Thermochemische Randschichthärteverfahren ermöglichen eine ausscheidungsfreie Einlagerung von Kohlenstoff bzw. Stickstoff innerhalb des austenitischen Mischkristalls. Im Zusammenhang mit einer Randschichtbehandlung thermisch gespritzter Schichtsysteme stellen die charakteristischen Strukturmerkmale eine bislang weitgehend unerforschte Einflussgröße für die Beurteilung von Diffusionsprozessen dar. Bei der Verarbeitung von randschichtgehärtetem Pulver durch Verfahren des thermischen Spritzens ist die Phasenstabilität des Spritzzusatzwerkstoffs von übergeordneter Bedeutung. Die beiden Möglichkeiten einer Verfahrenskombination werden für hochgeschwindigkeitsflamm- und atmosphärisch plasmagespritzte Schichtsysteme des Werkstoffs EN 1.4404 durch systematische Prozess- und Parametervariation eingehend betrachtet. Für die einzelnen Schichtsysteme werden Einflussfaktoren struktur- und prozessspezifisch sowie in Abhängigkeit vom Anreicherungsmedium erfasst und im Kontext der Massivwerkstoffreferenz eingeordnet. Die daraus abgeleiteten allgemeingültigen Aussagen zu verfahrenstechnischen Wechselwirkungseffekten ermöglichen eine anwendungsorientierte Verfahrensauswahl bzw. Entwicklungsstrategie.Thermochemical surface hardening enables a precipitation-free solvation of carbon or nitrogen on interstices of the austenitic crystal lattice. However, the interplay of the diffusion mechanisms with the structural properties of thermal spray coatings has not yet been understood. Thermal spraying of surface-hardened powders is a further opportunity, where the phase stability of the feedstock material is of crucial importance. A process and parameter study is conducted on high velocity oxy-fuel and atmospheric plasma spraying of AISI 316L considering both basic concepts. Structural and process-specific influence factors are examined for the different coating systems in comparison to the bulk material reference. Correlation effects are determined allowing for an application-oriented process selection or development strategy.
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Martinavičius, Andrius. "Structural and transport property changes in austenitic stainless steel induced by nitrogen incorporation." Doctoral thesis, 2010. https://tud.qucosa.de/id/qucosa%3A25579.
Full textAbstract:
The saturation of the near surface layers of metals with different elements is a powerful tool to change their surface properties. In this work, structure and transport changes induced by incorporation of large amounts of nitrogen at moderate temperatures (∼370−430°C) in austenitic stainless steel are investigated. The structural study of the plasma nitrided ASS has been carried out using a combination of global (X-ray diffraction, nuclear reaction analysis) and local probe techniques (Mossbauer, X-ray absorption near edge structure, extended X-ray absorption fine structure spectroscopies). It reveals that nitriding at moderate temperatures (∼400°C) results in the nitrided layer with Fe, Cr and Ni being in different local chemical environments: Cr in the CrN-like state, Fe in the Fe4N-like state, Ni in the metallic state. The results demonstrate that the incorporation of interstitial nitrogen destabilizes homogeneous distribution of the ASS constituents, which leads to the segregation of the elements into small zones rich in Cr and Ni and provide strong evidence that the decomposition is of a spinodal nature. These experimental findings contradict the widely accepted view that the phase formed during nitriding at moderate temperatures is a homogeneous supersaturated nitrogen solid solution.
The nitrogen atomic transport study has been carried out by using ion beam nitriding of single-crystalline stainless steel, and the issues of the influence of the crystalline orientation, nitriding temperature, ion flux and ion energy are addressed. The diffusion coefficients have been extracted from the fitting of the nitrogen depth profiles by using the trapping-detrapping model. It is shown that the crystalline orientation plays a significant role in nitrogen diffusion: the penetration depth is largest, intermediate and lowest for the (001), (110) and (111) orientation, respectively. The pre-exponential factor D0 varies by two orders of magnitude depending on the orientation, while the activation energy E is similar (∼1.1 eV) for the (111) and (110) orientations and higher for the (001) orientation (∼1.4 eV). It is found that the nitrogen ion energy and the flux have the effect on the nitrogen transport in the bulk with higher energies (or fluxes) showing larger diffusion coefficients. The ion energy effect is more pronounced for the (001) than for the (111) orientation, while the flux effect is similar in both orientations. In addition, the diffusivity during post-nitriding thermal annealing without ion irradiation is found to be independent of the crystalline orientation. The observed radiation enhanced diffusion and anisotropy are discussed on the basis of nitrogen incorporation induced changes in the matrix structure (ASS decomposition and formation heterogeneous structure), ion bombardment induced effects (defects, localized vibrations) and correlated diffusion.
Book chapters on the topic "S-phase, stainless steel, nitriding, carburising"
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Nishimoto, A., K. Ichii, K. Nakao, M. Takai, and K. Akamatsu. "S Phase Formation of Some Austenitic Stainless Steels by Plasma Nitriding." In Stainless Steel 2000, 289–307. CRC Press, 2020. http://dx.doi.org/10.1201/9780367814151-27.
Full textConference papers on the topic "S-phase, stainless steel, nitriding, carburising"
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"AN EFFECT OF ION-PLASMA NITRIDING ON THE MICROSTRUCTURE AND PHASE COMPOSITION OF ADDITIVELY-MANUFACTURED AISI 321 STAINLESS STEEL." In Fizicheskaya mezomekhanika. Materialy s mnogourovnevoy ierarkhicheski organizovannoy strukturoy i intellektual'nye proizvodstvennye tekhnologii. Tomsk State University, 2020. http://dx.doi.org/10.17223/9785946219242/350.
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