Study on failure mechanism of the coated carbide tool

During metal cutting process, cutting tools have to resist extreme heat, high pressure, abrasion, thermal shock and mechanical shock. Chemical stability and hardness of chemical vapor deposition (CVD) coated carbide tools are much better than that of the uncoated carbide substrate. However, the fracture toughness of CVD coated carbide tools is not as good as that of the uncoated carbide substrate. This paper analyses the failure mechanism of CVD coated carbide tools. Experimental results show that the failure of coated carbide tools is mainly caused by the formation and extension of surface crack. Coating thickness, coating materials, and substrate materials significantly affect the toughness of coated carbide tools. X-ray diffraction technique is applied to measure the residual stress in coating surface, and equations model are introduced to calculate the surface residual stress induced during coating process.