Simulation And Process Research On CVD Diamond Coating Deposition On Wire Drawing Interior Surface

Attributed to its high hardness and wear resistance, CVD diamond is an excellent wire drawingmaterial. It shows a broad application prospect in the wire drawing industry. In this thesis, substratetemperature field and flow field of HFCVD system were investigated using FEA method. Based onthe numerical analysis results, suitable fabrication process parameters of diamond-coated wiredrawings were obtained. Experiments of the deposition, polishing and drawing performance of thediamond coating were studied. The main work and results are as follows:1. Temperature distributions on interior surfaces of wire drawings were analyzed and effects ofdifferent filament parameters on it were investigated. Substrate temperature increases30℃~35℃withthe filament temperature increases100℃. Substrate temperature increases60~100℃with thefilament diametre increases0.2mm. Substrate temperature increases40℃as the filament amountincreases1. Substrate temperature increases20℃with the distance between two filaments or thedistance between the filaments and the substrate decreases1mm.2. Thermal-fluid coupling analysis was investigated with the vertically laid wire drawing model.The flow velocity distribution around the wire drawing and the temperature gradient between thefilaments and the substrate were obtained. Flow field around the wire drawing was analyzed with thehorizontally laid wire drawing model. Effects of different gas parameters on the gas flow velocitywere studied. Based on this, methods proposed to improve the gas state in the inner surface had weresuggested.3. Diamond-coating on the inner surface of differently pre-treated wire drawing was deposited..The coating component and micro configuration were analyzed using Raman spectroscopy and SEM.The results show that compact structure, high purity and uniform thickness diamond coating can befabricated.4. diamond-coated wire drawings were polished. Situations using different deposition parameterswere compared. The results show that the coating polishing performance can be improved by usinglower deposition temperature or higher proportion of CH4. Welding wire drawing experiments weredone with the prepared diamond-coated wire drawing. The coating was well integrated with thesubstrate, while the copper coated on the wire was broken off due to the less smooth inner surrface ofthe wire drawing.