Ultra-Fast Si-DLC Deposition using Non-Uniform High-Density Plasma Generated by Microwave Input from the Side of a Cylinder

When ultra-fast DLC coating is applied to a long cylinder using the microwave-sheath voltage combination plasma method, a non-uniform deposition rate distribution occurs because of attenuation of microwaves. The rate is especially inconsistent in the axial direction. To achieve a uniform deposition rate distribution, we considered that scanning of the substrate with respect to the microwave input area would be effective. For this study, using a non-uniform high-density plasma unevenly distributed on the side, Si-DLC was deposited by propagating microwaves from the side of a cylinder specimen. Also, Si-DLC was deposited using conventional DC plasma. The frictional properties obtained using the two methods were compared. When microwaves were used, Si-DLC was deposited at a maximum deposition rate of 85 μm/h near the contact point between the microwave input part and the cylinder specimen. The average hardness of Si-DLC measured from near the contact point to a position 25 mm distant along the cylindrical axis was 19.63 GPa. A reciprocating friction test was performed on the obtained Si-DLC with PTFE as the counter material under lubrication with PAO4. The coating method caused no difference in the friction coefficient: the dynamic friction coefficient was approximately 0.03. Next, a Si-DLC film was formed by scanning the cylinder specimen in the axial direction during high-speed film formation using microwaves introduced from the side of the cylinder specimen. Friction tests were conducted at several locations. The friction behavior showed no effect of deposition history differences caused by scanning.