Analysis of laser-nitrided stainless steel via nuclear methods

Abstract.

Laser nitriding of iron and other metals is governed by the complicated interplay of the laser–plasma–liquid surface interactions which lead to a superposition of several mechanisms. This article reports on the influence of the nitrogen gas pressure on the nitriding process for stainless steel. The effects of the nitrogen gas pressure on the nitrogen depth profiles and the phase formation are revealed by resonant nuclear reaction analysis, Mössbauer spectroscopy, and X-ray diffraction. We found that the surface nitrogen concentration reaches 10 at. % with a mean value of about 7.5 at. % in the first 150 nm. There seems to be a pressure window between 0.1 and 0.7 MPa for the most efficient treatment. In the surface layer, an additional γ-Fe(N) phase can be distinguished from the original γ-phase of the stainless steel.