Comparison of the oxidation behaviour of WC-Co and WC-Ni-Co-Cr cemented carbides

Resumen:
Thermogravimetric experiments confirm that the oxidation resistance of WC-Co and WC-Ni-Co-Cr alloys increases with their metallic content. This is due to the fact that, as the metallic content increases, the oxide scales present higher MWO(4) to WO(3) ratios and lower porosity. The good correlation found between the activation energies calculated by either the isothermal or the isoconversion method suggests that oxidation is controlled by surface chemical reaction. Activation energies increase with temperature between 650 and 800 degrees C for both WC-Co and WC-Ni-Co-Cr alloys. This increment is higher for WC-Co materials due to their tendency to form scales with higher tungstate contents.