Effects of Cr concentration on the microstructure and properties of WC-Ni cemented carbides

Based on thermodynamic calculations, WC-Ni-Cr3C2 model alloys with high Ni content have been designed by fixing the carbon potential to form either graphite or eta (M6C) phases. The solubility of the grain growth inhibitor Cr3C2 in the Ni binder phase has been experimentally determined by electron-probe microanalysis and compared with thermodynamic calculations. Five alloys with different Cr3C2 contents were prepared considering the observed solubility limit and compared with a Cr-free alloy. The effects of Cr3C2 addition on the microstructures, corrosion resistance, and mechanical properties of WC-Ni cemented carbides were studied using optical microscopy (OM), scanning electron microscopy, electrochemical examinations, and mechanical property tests. Our results indicate that an increase in the Cr3C2 concentration results in a decrease in both the density and the fracture toughness of cemented carbide samples. The maximum hardness was obtained with the addition of 0.75 wt.% Cr3C2. The corrosion resistance of WC-Ni cemented carbides in H2SO4 solution can be significantly improved with the addition of Cr3C2.