Interstitial hardening of duplex 2205 stainless steel by low temperature carburisation: enhanced mechanical and electrochemical performance

Kahn, H.; Heuer, A. H.; Michal, G. M.; Ernst, F.; Sharghi-Moshtaghin, Reza; Ge, Yindong; Natishan, Paul M.; Rayne, Roy J.; Martin, Farrel J.

doi:10.1179/1743294411y.0000000015

Cited by 20 publications

(12 citation statements)

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“…Low-temperature carburization or nitridation are effective ways to improve surface properties and corrosion resistance of stainless steels [7][8][9][10][11][12][13]. For PH 13-8 Mo stainless steel, a significant increase of surface hardness and corrosion resistance was achieved after low-temperature carburization [13].…”

Section: Introductionmentioning

confidence: 99%

“…As aging proceeds, the fractions of Ni and Al increases and the Ni-to-Al ratio approaches unity [2,3]. The NiAl precipitates are nanometer-sized, spherical, and coherent with the ferrite-or martensite matrix [6].Low-temperature carburization or nitridation are effective ways to improve surface properties and corrosion resistance of stainless steels [7][8][9][10][11][12][13]. For PH 13-8 Mo stainless steel, a significant increase of surface hardness and corrosion resistance was achieved after low-temperature carburization [13].…”

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NiAl precipitation in delta ferrite grains of 17-7 precipitation-hardening stainless steel during low-temperature interstitial hardening

et al. 2015

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a b s t r a c tInterstitial hardening via low-temperature carburization and nitridation has been studied in 17-7 precipitation-hardening stainless steel. During such interstitial hardening, nanometer-scale NiAl precipitates form in delta ferrite in the bulk, but not in the hardened surface layer. In the carburized ferrite grains, regions of NiAl stoichiometry could be identified, but cannot be identified as regions with a different crystal structure. In the nitrided grains, NiAl particles could neither be detected by corresponding changes in local composition nor by their crystal structure.Precipitation-hardening (PH) stainless steels are a family of stainless steels that combine high strength, ductility, and good corrosion resistance. They are widely used as structural materials in various industrial applications. Depending on the thermal history, alloys can contain variable amounts of austenite, ferrite, and martensite. Precipitation hardening in these steels is achieved by homogeneously dispersed fine precipitates formed during aging.PH stainless steels containing Ni and Al (like 17-7 and 13-8 Mo) can be age-hardened by the formation of NiAl particles (space group Pm 3m). The lattice parameter of stoichiometric NiAl at room temperature is 0.2887 nm, which is very close to the lattice parameter of the ferrite matrix (0.2881 nm in this study). The aging temperature of 17-7 PH stainless steel is above 773 K [1].Age hardening by NiAl was studied previously in several stainless steels. In the initial stage of NiAl precipitation, there are significant fractions of Cr, Mo, and Fe present in the precipitates [2-6]. As aging proceeds, the fractions of Ni and Al increases and the Ni-to-Al ratio approaches unity [2,3]. The NiAl precipitates are nanometer-sized, spherical, and coherent with the ferrite-or martensite matrix [6].Low-temperature carburization or nitridation are effective ways to improve surface properties and corrosion resistance of stainless steels [7][8][9][10][11][12][13]. For PH 13-8 Mo stainless steel, a significant increase of surface hardness and corrosion resistance was achieved after low-temperature carburization [13]. Interestingly, a thin carbidic layer formed on the carburized surface. However, there was no report of NiAl formation.Low-temperature carburization and nitridation have also been successfully applied to 17-7 PH stainless steel [14,15]. The ferrite phase in the alloy responds to such interstitial hardening in a very unique and unusual manner, leading to a weak-contrast appearance in conventional transmission electron microscopy (TEM) images. Nanometer-scale NiAl precipitates were observed in the ferrite grains in the bulk but absent in the weak-contrast grains [14].In the present work, we investigate the effect of lowtemperature carburization and nitridation on the formation of NiAl precipitates in the ferrite phase of 17-7 PH stainless steel. 17-7 PH stainless steel in condition A [1] was provided by AK steel in the form of 3 mm thick plates. The nominal composition is 17-19 at.% Cr, ...

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NiAl precipitation in delta ferrite grains of 17-7 precipitation-hardening stainless steel during low-temperature interstitial hardening

et al. 2015

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“…[12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] As implied by the name, carbon and nitrogen reside in interstitial lattice sites. The surface alloyed region, the case, ranges in thickness between 5 and 30 μm depending on treatment time and temperature.…”

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“…19,21 In previous work, it was shown that the inherently good pitting resistance of DSS alloy 2205 was retained while increasing the crevice corrosion and fatigue resistance. 25 The inherent pitting resistance (high value of Epit) of alloy 2205 is a result of high concentrations of passivity-promoting alloying elements. As discussed above, when a stainless steel becomes sensitized, the alloying elements (i.e., Cr) that provide passivity, in addition to being strong carbide formers, are depleted in the regions adjacent to where the new phases form.…”

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“…Interstitial hardening of a number of stainless steels, including austenitic, martensitic, and duplex, has been shown to improve the hardness and wear, fatigue, galling, and corrosion resistance. [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] IH treatments have been shown to be effective in improving the pitting resistance in stainless steels with Cr concentrations as low as 13 at%. 19,21 In previous work, it was shown that the inherently good pitting resistance of DSS alloy 2205 was retained while increasing the crevice corrosion and fatigue resistance.…”

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Communication—Restoring the Pitting Resistance of Sensitized Duplex Stainless Steel Using Interstitial Hardening

Tailleart

Martin

Rayne

et al. 2016

J. Electrochem. Soc.

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Cast duplex stainless steel, alloy 2205, a mix of ferrite and austenite, was heat-treated at 845 • C which produced additional phases, e.g., sigma and chi. The new phases depleted the surrounding grains of passivity-promoting elements such as Cr, causing alloy sensitization and a corresponding decrease in pitting resistance. A low temperature gas-phase interstitial hardening (IH) surface modification process was used to surface alloy sensitized samples. Anodic polarization curves showed that after IH treatment, the pitting resistance, determined by the pitting potential, of sensitized samples was restored to values of the as-cast material. Duplex stainless steels (DSS), a mix of ferrite and austenite, are finding applications in the oil and gas, chemical, food and beverage, power, transportation, and paper industries 1-5,10,11 because of their good corrosion resistance and mechanical properties. However, when DSS are exposed to temperatures between 650• C and 950• C, additional phases, e.g., sigma and chi, form. The formation of these phases results in a depletion of passivity-promoting elements, e.g., Cr, in the surrounding grains, resulting in sensitization and decreased corrosion resistance.1-11 The Cr concentration in the depleted regions has been reported to be in the range of 12.5 to 19.5 at%. 5,8,9 In recent years, low temperature (generally lower than 500• C, but alloy dependent) surface modification processes using gas or plasma interstitial hardening (IH) have been developed for introducing substantial amounts of carbon and/or nitrogen (generally between 10 to 15 at%) into stainless steels without the formation of detrimental carbides or nitrides. [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] As implied by the name, carbon and nitrogen reside in interstitial lattice sites. The surface alloyed region, the case, ranges in thickness between 5 and 30 μm depending on treatment time and temperature. To form a case, strong carbide/nitride forming elements, such as Cr, are essential (for example, References 13,16,18,22). Interstitial hardening of a number of stainless steels, including austenitic, martensitic, and duplex, has been shown to improve the hardness and wear, fatigue, galling, and corrosion resistance.12-26 IH treatments have been shown to be effective in improving the pitting resistance in stainless steels with Cr concentrations as low as 13 at%. 19,21 In previous work, it was shown that the inherently good pitting resistance of DSS alloy 2205 was retained while increasing the crevice corrosion and fatigue resistance. 25 The inherent pitting resistance (high value of Epit) of alloy 2205 is a result of high concentrations of passivity-promoting alloying elements. As discussed above, when a stainless steel becomes sensitized, the alloying elements (i.e., Cr) that provide passivity, in addition to being strong carbide formers, are depleted in the regions adjacent to where the new phases form. This communication discusses the application of IH to restore the pitting corrosion resistance ...

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Effects of Alloying Elements and Microstructure on Stainless Steel Corrosion: A Review

Sun

Tang

Wang

et al. 2021

steel research int.

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Stainless steel has attracted significant attention in industrial and engineering applications. To improve its corrosion resistance, there are two major approaches that are to optimize the elemental composition and tune the microstructure. A comprehensive review of the main findings on the corrosion of stainless steel is presented, and some controversial issues are highlighted. First, the functional roles of alloying elements are discussed, including nonmetallic (B, C, and N) and metallic (Cr, Ni, Cu, and Mo) elements. Additionally, their detrimental and positive effects, as well as the corresponding mechanisms, are highlighted. Second, the microstructure‐induced corrosion of stainless steel is discussed, including the crystallographic‐orientation‐dependent corrosion, the dual influence of grain size and grain boundary distribution, texture, and defects in the matrix. In addition, nanostructured materials are mentioned herein. Third, challenges as well as research trends in the future are proposed with perspectives for the development of novel stainless steel in research and industrial applications.

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Interstitial hardening of duplex 2205 stainless steel by low temperature carburisation: enhanced mechanical and electrochemical performance

Cited by 20 publications

References 19 publications

NiAl precipitation in delta ferrite grains of 17-7 precipitation-hardening stainless steel during low-temperature interstitial hardening

NiAl precipitation in delta ferrite grains of 17-7 precipitation-hardening stainless steel during low-temperature interstitial hardening

Communication—Restoring the Pitting Resistance of Sensitized Duplex Stainless Steel Using Interstitial Hardening

Effects of Alloying Elements and Microstructure on Stainless Steel Corrosion: A Review

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