Mechanical Preparation Procedure for Characterizing by EBSD the Crystallographic Orientation in Surface Layers of Austenitic Stainless Steels Plasma Nitrided

Abstract

This contribution reports on an experimental polishing procedure, that is comprised of early grinding in Al₂O₃ slurries and late polishing in colloidal silica, which is used for preparing the nitrided region of a plasma nitrided austenitic stainless steel, for crystallographic analysis via electron backscatter diffraction (EBSD). The suitability of the polished surfaces for conducting EBSD characterization was assessed through an analysis of both the surface roughness (appraised by atomic force microscopy) and the quality of the Kikuchi diffraction patterns. We observed that as-nitrided virgin surfaces were not suitable for EBSD characterization, due to intense surface roughening, which was induced by the nitriding process itself. At the subsurface region, exposed by on-top mechanical polishing, the flatter nature of the polished surfaces allowed the acquisition of EBSD patterns with enough quality for microtexture analysis. A resolution of 100 nm in the total removed layer was attainable via careful control of the polishing parameters. Close parallelism between the polished and original surfaces was verified.

Keywords:
Electron backscatter diffraction; orientation imaging microscopy; metallography; scanning electron microscopy; mechanical polishing