Fundamental and innovations in plasma assisted diffusion of nitrogen and carbon in austenitic stainless steels and related alloys

Abstract

An improvement of the surface properties of austenitic stainless steels and nickel-based alloys is obtained by low temperature plasma assisted nitriding (PAN), plasma assisted carburizing (PAC) and plasma assisted nitrocarburizing (PANC). At low temperature, PAN treatment produces a peculiar phase usually called expanded austenite, S phase, m phase or γN phase. Replacing nitrogen by hydrocarbon for conducting a low temperature PAC gives a carburized layer containing the carbon expanded austenite phase (γC). These two phases can simultaneously be obtained by combining hydrocarbon and nitrogen in the gas phase through a low temperature PANC. Several fundamental aspects concerning the expanded austenite phases are presented in this paper. A figure is presented. © 2009 Wiley-VCH GmbH & Co. KGaA, Weinheim.