Influence of temperature, grain size and cobalt content on the hardness of WC-Co alloys

Abstract

The Vickers hardness of WC-Co alloys has been measured at temperatures ranging from -196 to 900 degrees C. The cobalt content of the alloys ranged from 10 to 24 vol% and the grain size from 0.5 to 2.3 um. It was found that, at all cobalt contents and all temperatures, the decrease in hardness with increasing grain size can be approximated by a Hall-Fetch type relationship. Up to about 600 degrees C the decrease in hardness with increasing temperature appears to be due mostly to the decrease in the intrinsic hardness of the individual phases. Above 600 degrees C the decrease in hardness appears to be due mostly to easier slip transfer across grain boundaries. Finer grained alloys have been found to preserve their hardness at high temperature better than coarser grained alloys, at all cobalt contents.