The WC composite powder was synthesized by a new specific chemical activation technique. A large number of lattice defects such as surface humps, dislocations and stacking fault exist in the surface of the WC powder after chemical activation technique. By using such activated WC powder, the binderless WC cemented carbide with high density (15.54 g/cm3), super hardness (average 26.29 GPa) and excellent fracture toughness (8.9 MPa.m1/2) can be fabricated by SPS at 1700 °C and 50 MPa pressure. The improvement in density, hardness and fracture toughness are respectively 4.5%, 15.3% and 17.1% compared to when using the original WC powder. This improvement is because microscopic defects on the surface of the WC powder can greatly improve surface free energy of the powder, which improves the sintering activity and reduces the sintering temperature of the WC powder.

The measuring temperature test, measuring force and failure test were carried out in order to research failure mechanism of cemented carbide milling insert machining heat resistant steel of 3Cr1Mo1/4V. The falling process of sticking-welding chip was observed by high-speed photograph.The failure morphology was observed and analyzed by SEM. The test result showed that adhesive failure and fatigue failure were the main invalid form. The mathematical model of adhering failure depth was built and the finite element analysis of the thermal-mechanic coupling physical field was conducted based on the milling equipment. The research result illustrated that the temperature of the cutter-chip contact region affectes the depth of adhering failure and they are no-linear positive correlation. The thermal-mechanical coupling equivalent stress inhances with the increase of temperature. The cutter will bring about fatigue failure when it adds over ultimate strength of cemented carbide.