The metastable m phase layer on ion-nitrided austenitic stainless steels Part 2:: crystal structure and observation of its two-directional orientational anisotropy

The single phase formed by ion nitriding austenitic stainless steels for short times and at low temperatures has variously been identified in the literature as the S, epsilon' or m phase, but a definitive study has yet to be performed. In this work we confirm the tetragonal structure reported previously by ourselves and by Angelini et al. [E. Angelini, A. Burdese, B. DeBenedetti, Metall. Sci. Technol. 6 (2) (1998) 33] ], and we discuss the alloy chemical context of the m-phase in terms of a structure lying between the fee (Cu type) and bcc (W type) host metal structures. Further, pole figure results are presented which show evidence of a pronounced [101] texture normal to the surface and an unexpected strong (112)-pole in-plane anisotropy. (C) 1999 Elsevier Science S.A. All rights reserved.