Effect of different nitrogen pressure sintering on surface structure and properties of WC-TiC-NbC-Co cemented carbide

WC-TiC-NbC-Co alloy was prepared by sintering at different nitrogen pressure, and then CVD coating was carried out. Scanning electron microscope (SEM), energy dispersive spectrometer (EDS), X-ray diffraction analyzer (XRD), surface roughness analyzer and scratch tester were used to characterize and measure the surface morphology, composition, phase, roughness and coating adhesion of sintered and coated samples. The results show that the surface of WC-TiC-NbC-Co cemented carbide samples sintered in nitrogen atmosphere forms a gradient layer dominated by TiC phase compared with vacuum sintering, and the thickness of the gradient layer increases with the increase of nitrogen pressure. When nitrogen pressure is 15 kPa, the thickness of gradient layer reaches 10μm. When nitrogen pressure is 10 kPa, the sample gets the best adhesion to CVD coating. It is shown that a certain thickness gradient layer can be formed on the surface of the alloy under appropriate nitrogen pressure, and the adhesion of the coating can be improved.