Evolution of microstructure and high temperature hardness in WC_xTaC-Co cemented carbides

Influence of TaC addition with 0.00% to 3.00% (mass fraction) on the microstructure, mechanical performance and high temperature hardness was investigated through SEM, XRD, EPMA analysis and mechanical tests including high temperature hardness measurement. The results show that when the mass fraction of TaC is less than 0.50%, TaC is mainly dissolved in the bond phase, strengthening the solid solution and inhibiting the grain growth, and the Vickers hardness and the bending strength of the alloy at room temperature are obviously improved. When the mass fraction of TaC increases from 0.50% to 3.00%, the unevenly distributed (Ta, W) C precipitated phase begins to appear in the structure, and the Vickers hardness of the alloy at room temperature increased slowly, while the bending strength increased slowly and then decreased. The addition of TaC helped to enhance the hardness of cemented carbide at high temperature, and the effect of improvement was positively related to the amount of TaC added. At 1000℃, the high temperature hardness of the alloy without TaC was only 802 MPa, while the alloy with a mass fraction of 1.50% TaC improved the hardness of the alloy at high temperature, and its high temperature hardness could reach 1 025 MPa.