Effect of chromium doping on the grain boundary character of WC-Co

The life of cutting tool inserts is critically important for efficient machining, reducing manufacturing cost, embedded energy, and enabling more complex parts to be machined. For these applications, cemented carbide (WC-Co) materials are a prime candidate. The performance of these materials can be limited by early fracture, typically via an intergranular fracture path with respect to carbide grains. This motivates further studies to understand the character of the grain boundary network so that grain boundary engineering (GBE) of WC-Co tools can be used to improve tool life and performance. In this work, we have used Rohrer et al.'s five-parameter grain boundary character distribution (GBCD) analysis to examine the grain boundary network of WC-10wt%Co and WC-10wt%Co-1wt%Cr samples (Rohrer et al., 2004a [1]). It was found that the measured area fraction of the Sigma 2 boundaries was comparable to the values reported in the literature despite the relatively larger grain sizes (similar to 14 mu m) and higher cobalt contents. The result suggests that chromium doping increases the area fraction of Sigma 2 boundaries from 12.8 % to 14.8 %. It is proposed that this is a consequence of altering the Sigma 2 boundary energy, as associated with adding chromium.