The change of surface microstructure of gradient cemented carbide directly affects the machining performance of CVD coated cemented carbide tools, while the change of sintering temperature will significantly affect the surface and core microstructure of gradient cemented carbide

The effect of three sintering temperatures (14101440 ℃ and 1460 ℃) on the surface layer of gradient cemented carbide (0~100 μ m) The influence of microstructure and mechanical properties of gradient cemented carbide was studied. The surface microstructure, gradient zone and grain size of alloy core were analyzed by SEM and EBSD, The thickness of the gradient layer increases. The grain size of the hard phase (WC and cubic solid solution phase) of the alloy increases significantly with the increase of the sintering temperature. The grain size of WC in the gradient zone is larger than that of WC in the core, and the difference between the two increases with the increase of the sintering temperature. The growth rate of the cubic solid solution in the core is higher than that of WC. With the increase of the sintering temperature, the magnetic force of the alloy decreases by 10.3%, and the fracture toughness and bending strength of the alloy increase by 8.5% and 7.7%, respectively, compared with the samples without the gradient layer, The bending strength of the alloy specimen with gradient layer retained at three sintering temperatures increased by 7.6%~9.8%

The microhardness of the alloy from the surface to the core first decreased to the lowest point and then gradually increased to close to the core hardness. The lowest point of HV in the gradient layer was about 87% of the core HV. With the increase of sintering temperature, the HV in the gradient zone and the core showed a downward trend