THE MECHANISM OF SURFACE SEGREGATION BY THE METHOD OF MECHANICAL POLISHING

Mechanical polishing and subsequent thermal oxidation are the indispensable condition for rapid formation of a continuous and highly Cr-enriched layer on the surface of a Ni-Cr alloy. Direct observations of the Cr distribution on the surface by Auger map show a possible process for Cr segregation. The huge amount of grain boundaries created by mechanical polishing promote the upward diffusion of Cr. Selective oxidation and Cr-holding effect also speed up the formation of Cr₂O₃.