Preparation Of CVD Diamond Coated Rotating Tools

Diamond film used as a coating is important for machining difficult-to-machine materials such as CFRP(Carbon Fiber Reinforced Polymers)and MMC(Metal Matrix Composite).Diamond film has advantage of high hardness,high wear resistance,low friction coefficient,high thermal conductivity,etc.Cemented tungsten carbide has advantage of high toughness and low cost.Diamond coated tools which combined with their advantages become an ideal tool for machining.Diamond coated tools used to deposited under condition of one deck of filaments,which results in rapid temperature decrease along the substrates and short coating length.What needed to solve is lengthen coating length.In this thesis,H2 and methane(CH4)were used to deposit diamond film on cemented carbide tools by Electron-assisted hot filament CVD(EA-HFCVD),using two deck filament structure.Scanning electron microscopy(SEM)and Raman Spectro-scopy are performed to characterize the morphology and quality of deposited films.The conclusions are as follows:(1)Temperature can decrease more slowly by arranging filaments structure more rational.Filaments can supply energy more stably by changing carbonization parameters.(2)Experiments prove that high quality diamond coating can be deposited on cement carbide tools under condition of double-deck filaments.The results of diamond films show that coating length is longer and deposition rate is greater than one deck filament.(3)Temperature has a great influence to diamond morphology.Because of the highest temperature of the top of drills,diamond thin films have the best quality and clear facets.Raman spectra shows that the film is mainly made of diamond.Temperature decrease along the drill axis and diamond morphology changes from granular to cluster,decreasing in size as well.