Development of nitride-layer of AISI 304 austenitic stainless steel during high-temperature ammonia gas-nitriding

Recent Developments on Discontinuous Precipitation

“…They observed the DP of Cr 2 N nitride lamellae in high-nitrogen Cr-Mn austenitic stainless steel after ageing and lamellar M 23 C 6 carbide in Cr-Ni austenitic stainless steel. Moreover, studies of Peng et al [62] reported for the AISI 304 austenitic stainless steel after nitriding at high temperature (>1073 K) a coarse lamellar structure of austenite and Cr 2 N which was developed in the front of fine lamellae composed of austenite and CrN.…”

“…Major elements in the nitride (between 0-and 1-nm markers) are Fe, Cr, and nitrogen, concentrations of which are about 23, 36, and 23 at.%, respectively. Wang et al [62] concluded based on electron diffraction data that the nitride phase at the interface is face-centered cubic (fcc), most likely rocksalt-structured (Cr, Al, Fe) N 1-X . Therefore, the cellular precipitation reaction can be written as γ N → β + α where γ N is the nitrogen-supersaturated austenite, β is MN 1-X , and α is the ferrite with α minimum nitrogen concentration.…”

Effects of Gas Nitriding on the Mechanical and Corrosion Properties of SACM 645 Steel

“…Therefore, various methods, such as nitriding, carburizing, ceramic coating and thermal chemical treatments, have been devised to improve the surface mechanical properties of the components [3][4][5]. Among those surface treatment processes, the gas nitriding methods have been used extensively to enhance the mechanical properties of steel components [5][6][7][8][9][10][11][12][13]. During the gas nitriding treatment, nitrogen, which is provided by the catalytic dissociation of ammonia, diffuses through the steel surface to form a concentration gradient as well as nitride precipitates in the nitriding case.…”

“…According to the nitriding condition and notch shape, the improvement of the fatigue characteristics of the notched specimens was more effective than unnotched specimens. Peng [11] investigated ammonia-gas nitriding on AISI 304 austenitic stainless steel at temperatures higher than 800˚C. The result from Peng showed that a metas phase named 'S-phase' or 'γ N -phase' (expanded austenite) was formed at such high temperatures due to a sufficiently high nitriding potential of ammonia gas.…”

Estudio del efecto de una atmósfera gaseosa de amoniaco en un componente de un reactor catalítico fabricado en acero inoxidable AISI-SAE 304

“…Diversos estudios han mostrado que la nitruración por gas de aceros inoxidables austeníticos a temperaturas convencionales de 500 o C a 650 o C resulta en la formación de nitruros de Cromo que puede conducir a un deterioro de las propiedades de corrosión, aunque se incrementa significativamente la resistencia al desgaste, por lo que se han llevado a cabo diversas aproximaciones para reducir la formación de estos nitruros en estos materiales y en el rango de temperatura mencionado [3].…”