Conditions for the formation of a martensitic single-phase compound layer in ion-nitrided 316L austenitic stainless steel

摘要

The formation of a single phase structure (m) in an ion-nitrided 300 series stainless steel was confirmed by X-ray diffraction, microprobe and microhardness profiles. The m phase has a depth-dependent, variable nitrogen content between 30 and 20 at. pet. N (with increasing depth). A time-temperature (t-T) map of m phase formation upon treatment in 65% N-2, 35% N-2 is presented for 316L steel, The m phase forms at nitriding temperatures up to 510 degrees C but occurs as a single phase only up to 480 degrees C; at higher temperatures and by long treatment times, m is destabilized in favor of gamma' + CrN. A tetragonal (martensitic) structure for m previously reported in the literature remains tentative. (C) 1998 Elsevier Science S.A. [References: 6]