Develop Of Polishing Plate Used In Dynamic Friction Polishing Of Diamond

Diamond processes excellent properties, such as highest hardness, high thermal conductivity, wide-range transparency, low friction coefficient, strong chemical inertness. It has wide application prospects in high-tech fields like optics, thermology, acoustics and electronic semiconductor. However, diamond films have low surface flatness which prepared by chemical vapor deposition (CVD). The height difference from peak to valley is up to80-100μm on the surface of the diamond films. Therefore, diamond films must be polished to meet the application’s requirements. Diamond is one of the most difficult machining materials in the nature due to its highest hardness, excellent chemical inertness and other properties. There are many polishing technologies at present, such as mechanical polishing, thermo-chemical polishing, dynamic friction polishing, chemically assisted mechanical polishing, laser polishing, ion-beam polishing and so on, but there exist problems like low efficiency, poor surface quality, high cost, etc. In the process of preparing and polishing diamond films, an advanced processing technology requires separating rough polishing process and fine polishing process, the roughing stage is to obtain high material removal efficiency and the fine finishing stage to get smooth surface. Dynamic friction polishing based on thermochemical reactions is a potential method in diamond polishing; it has high material removal efficiency and low equipment cost.This paper aimed at solving the problems like low material removal efficiency and high wear rate of polishing plate in dynamic friction polishing. Basing on the diamond graphitization theory and the polishing plate material requirements, it selected seven different material prescriptions, Invar, Amorphous Fe48alloy, Inconel600, NiCrFe alloy, MnCu alloy, MnNi alloy and WMoCr alloy, prepared polishing plate material using mechanical alloying and spark plasma sintering, and carried out polishing experiments. Results show that the WMoCr alloy had the highest material removal efficiency (about1.5μm/min) and the lowest wear rate of polishing plate (about0.35mm3/min); the MnNi alloy also had high material removal efficiency (about1.45μm/min) but with severe wear; the amorphous Fe48alloy was crystallized and had seriously severe wear during polishing. There was no mechanical crushing during polishing showing in further analysis of polished diamond films, WMoCr alloy polishing plate and the microstructure and phase composition of debris. Diamond were removed by chemical reaction through generating non-diamond carbon, metal carbide, metal carbon-oxygen complexes, which provided evidences for the theory analyzed of diamond graphitization. The process and mechanism of dynamic friction polishing could be described as follows:under the synthetic effect of friction heat and catalytic metal, diamond conversed into non-diamond carbon which was removed by the combined effects of thermochemical diffusion, oxidation and mechanical friction finally.