Research On Preparation And Adhesion Performance Of Diamond Coating For Cutting Tool By Using PVD Interlayer

CVD diamond coated cutting tool has been a hot issue in the field of coated tool from the1980sdue to its outstanding cutting performance. The research of CVD diamond coated cutting tool has got agreat progress in recent30years. In some developed countries, the technology which diamond film isdeposited on hart-metal containing no more than6%cobalt has been much perfect. In China, theequipment of producing batch of diamond coated tools has some gap comparing with abroad.However，the poor toughness of this kind of cutting tool is a enormous obstacle for its wildlycommercial application. With increasing cobalt contain the toughness and strength of hard-metal isimproving significantly. So the hard-metal containing more than10%cobalt has a wider application.In this paper, CVD diamond coating deposition on hard-metal containing10%cobalt has beenstudied. The content can be summarized as follows:1. The process of the cementation depositing copper has been studied. The proper CuSO4concentration and treatment duration is selected. The process of the cementation has beenoptimized. Deposition of CVD diamond thin film on hard-metal after cementation has beenanalyzed. The results show that diamond can be deposited on copper, but the graphitealways appears before deposition diamond. The adhesion of diamond is so bad.2. The metal interlayer, such as Chromium, has been made with physical vapor deposition(PVD). Relationship between the sputtering parameters and depositional rate was studied.Factors such as the sputtering parameters and surface roughness which affect the bindingforce of interface of films and substrate were discussed. With increasing gas pressure, theadhesion has been worse. With increasing substrate temperature, the adhesion was improvedat first, and then reduced. The adhesion was improved with the appropriate roughness,however, the adhesion would be weeked for much too high roughness. These achievementcan guide the preparation of the interlayer on hard-metal.3. A new pretreatment,“Two-step method and then sputtering interlayer”, at WC-10%wtCowere studied. Relationship between etching time and CVD diamond film are systematicaldiscussed. Diamond nucleation and growth based on the transition layer, Niobium forexample, are analyzed. Relationship between substrate temperature and diamond depositionis studied. The diffusion of cobalt is measured by Energy-dispersive X-ray spectroscopy (EDS). This pretreatment method is superior to just two step or sputtering interlayer. Thediamond nucleation was not only increased, but also the quality of diamond film wasimproved.4. The adhesion of the diamond coatings was qualitatively estimated by performing Rockwellindentation tests. Process conditions such as corrosion time, substrate temperature,annealing treatment and metal transition layer which affect the adhesion of the diamondfilm are analyzed. Proper corrosion time can improve adhesion strength. The process withannealing diamond film for2hour in vacuum brings negative affect on adhesionperformance. The adhesion strength with substrate temperature for790℃is better than for750or830℃. Compared with two-step pretreatment, adhesion performance was improvedfor sputtering metal interlayer after two–step treatment.