Research On Lapping α-sapphire By CVD Diamond Coated Tool

With high hardness and strength, high transmittance for visible and infrared light, high thermal impact resistance and electric insulation property, sapphire(α-alumina,Al2O3) has been widely used in national defense, aerospace, living and industry fields. However it has become the primary problem of sapphire application for its low machining efficiency by traditional lapping process. Chemical vapor deposition(CVD) diamond coated cutting tool is the most ideal tool for the processing of nonmetallic hard and brittle materials efficiently because of its excellent cutting performance such as surface high hardness, abrasion resistance, high melting point, chemical stability.Aiming at improving lapping efficiency of sapphire, CVD diamond coated cutting tools with different morphologies were introduced during sapphire lapping process in this thesis. The main work and results are as follows:(1) The deposition technology of CVD diamond coated tools with different morphologies by HFCVD method and influence of deposition parameters on CVD diamond morphology were studied. By controlling deposition parameters, three kinds of CVD diamond coatings with different morphologies were prepared on cement carbide tools. The morphologies are spherical structure, incisive pyramid and quadrangular prism.(2) The mechanical and chemical mechanism of CVD diamond coated tool lapping with sapphire was investigated. The removal model of single diamond particle for sapphire lapping by CVD diamond coated tool was established. The material removal rate(MRR) and tangential force of CVD diamond coated tools with different morphologies was researched. The surfaces of coated tool after lapping were characterized by SEM, EDS and Raman spectroscopy. The chemical mechanism during lapping was studied.(3) The effect of process parameters on material removal rate and surface roughness was investigated by lapping experiments. The results show that the MRR can reach 2.55μm/min and the surface roughness is 0.369μm by using process parameters of high lapping efficiency. By using the optimal parameters for surface roughness, the MRR of 1.68μm/min and the surface roughness of 0.271μm are obtained.