The enhancement of the microstructure and mechanical performances of ultrafine WC-Co cemented carbides by optimizing Cr2(C,N) addition and WC particle sizes

Abstract

Ultrafine WC-10Co cemented carbides with different Cr2(C,N) inhibitor contents and different-scaled WC powders were prepared by low-pressure sintering. Their influence on the microstructure and mechanical performances were investigated and expounded in this work. The result shows that the Cr2(C,N) addition homogenized the microstructure of the cemented carbides and refined WC grains. With the Cr2(C,N) addition increasing, hardness increased to 1870 kg/mm2, transverse rupture strength (TRS) first increased to 4435 MPa and then sharply decreased to 3230 MPa due to the existence of more pores with excessive Cr2(C,N). With the reduction of WC particle size, the mean WC grain size and mean free path of Co phase decreased, while the contiguity of the WC grains increased. The hardness and TRS of the specimens reduced, while fracture toughness increased. The comprehensive mechanical properties namely the TRS, hardness, and fracture toughness in the cemented carbides with 0.5 wt% Cr2(C,N) and 0.4 μm WC powder, were 4748 MPa, 1786 kg/mm2, 10.1 MPa· m1/2, respectively. A good combination of high TRS and hardness could be obtained in the cemented carbides by adopting appropriate amount of Cr2(C,N) and reducing the WC particle size.