The effects of metallic additives on the microstructure and mechanical properties of WC-Co cermets prepared by microwave sintering

Abstract

The present work investigated the effects of Mo and Si metallic powders on the microstructure and mechanical properties of WC-5wt%Co cermets prepared through fast microwave heating process. Accordingly, 5 wt% Mo and 5 wt% Si were added separately to the WC-Co cermet and intensive mixing was performed using a high-energy ball mill. The prepared samples were sintered at 1400, 1500 and 1600 °C without any soaking time. The XRD patterns demonstrated WC peaks as the dominant crystalline phase along with tiny peaks that could be attributed to the formed carbides and intermetallics as the reaction product. As expected, the mechanical properties of the cermets were improved by increasing the sintering temperature due to the increased density; then porosity was decreased. WC-Co-Si cermet sintered at 1600 °C obtained higher hardness (15.8 ± 0.1 GPa), bending strength (876 ± 16 MPa) and fracture toughness (15.8 ± 0.1), as compared to the WC-Co-Mo cermet, due to the lower eutectic temperature of the Co–Si binary phase in comparison to that of Co–Mo. Moreover, the microstructural investigations confirmed the formation of carbides and intermetallics with an almost uniform distribution of the phases in the composites.