Development Of Wheel For CVD Diamond Thermo-Chemical Polishing

Diamond is widely applied in many fields due to its excellent performances in mechanics, thermodynamics, optics, semiconductor and chemical inertness. Development of CVD diamond has solved the problems of sparsity and costliness. Meanwhile the low surface quality caused by tropistic growth limits its directively application. Consequently polishing of CVD diamond is a key technics in this industry.Researches on polishing of CVD diamond have been investigated by many people and a variety of methods have been advanced. The thermo-chemical polishing exhibits unique potential. During the thermo-chemical polishing, the carbon of diamond can diffuse into the metals and be graphited, by which the diamond can be polished. The thermo-chamical method has high efficiency, but the polishing wheel has poor morphology due to its low abrasion resistance under the rigorous condition, which leads to low surface quality of films.The FeAl alloy polishing wheel with high temperature intensity was developed for thermo-chemical polishing. The main contents include:(1) Novel intermetallic alloy (FeAl alloy) was proposed to be the material for thermo-chemical polishing wheel. FeAl alloy wheel was developed by powder metallurgy. The alloy powders were prepared by ball milling. The effection of milling parameters on alloying was studied through XRD spectrum and the results showed: ball to material raito was 10:1, process control agent was heptane 30ml, fine powders could be obtained after 60 hours milling.(2) The final polishing wheel was fabricated by hot-pressure sintering, and the influences of temperature, pressure on sintering were studied. Moreover the effections of milling time and additives TiC on hardness were researched. Results showed that the sintering and holding temperatures should be 1200℃and 600℃respectively, the pressure should be 6t, suitable amount of TiC could improve the hardness of the wheel.(3) Thermo-chemical polishing tests were carried out between FeAl alloy wheel and 304 stainless steel wheel. FeAl alloy wheel showed outstanding abrasion resistance, its abrasion was 13.9% of 304 stainless steel wheel and diamond volume polished by FeAl alloy wheel was 2.63 times as 304. (4) According to the microtopography, FeAl alloy wheel could keep the surface appearance well because of its high temperature intensity, stiffness and oxidation resistance. On the contrary, 304 stainless steel wheel had more abrasion due to its low intensity.