Microstructure Evolution in the Cemented Carbides WC-Co II. Cumulated Effects of Cr Additions and of the C/W Ratio on the Crystal Features of the WC Grains

Abstract

The influence of an addition of Cr, introduced to replace 5 at% Co on the microstructure evolution of WC-13 at% Co with different C/W ratio is examined at 1450 °C. Three alloys consisting of WC and Co binder and containing a graphite or η excess are studied by SEM and TEM. The effects of Cr are similar to those induced by a W excess in the undoped alloys: decrease of the mean grain growth and change of the interface features of the WC grains. The interface modification — less faceted, with steps — indicates a decrease of interface energy anisotropy and suggests a coarsening mechanism limited by the growth of the steps. The specific role of Cr on the hindrance of large grain formation depends on the C/W ratio.