Impact of surface preparation on the formation of deformation-induced α'-martensite in a metastable austenitic steel

The metastable austenitic steel X6CrNi-Nb18-10 (AISI 347) will partly transform to alpha'-martensite under mechanical loading at room temperature. In order to determine the influence of loading conditions on deformation-induced martensitic transformation, a thorough surface preparation is required for the samples to be analyzed, ensuring that a martensite-free sample surface is achieved prior to mechanical loading. In this paper, two preparation techniques were compared, focusing in particular on the final preparation step, which is polishing. Measurements using electron backscatter diffraction (EBSD) have revealed that large alpha'-martensite volume fractions of more than 20 % are present on the prepared sample surface after vibratory polishing. However, they can be removed almost completely by electrolytic polishing and chemical etching respectively.