Design On Deposition System And Tribological Properties Ofrf Magnetron Sputtered SiC-Al Coatings

Al-doped Si C(Si C-Al) coatings with outstanding properties have been deposited on substrates(Ti-alloy) by the ultrahigh vacuum Physical Vapor Deposition system which is designed and fabricated by our own. Al is used both as intermediate layer and doping element in order to solve problems of the poor interfacial adhesion between films and substrates and the high friction coefficient of Si C coatings, respectively. On the other hand, the simplification of depositional process and equipment generated by this technique makes it possible to complete the whole depositional process in our dual-target unbalanced magnetron sputtering reactor, which could be a stable solution to deal with the wear problem of Ti-alloy.In order to better meet the further requirements of studying films as rigid protective coating, a Radio Frequency Magnetron Sputtering Physical Vapor Deposition(RF-MS PVD) system was fabricated accorading to associated techniques and practical experience. A three-stage ultrahigh vacuum system composed of rotary vane pump and diffusion pump in parallel with TSP( titanium sublimation pump) was designed mainly for getting limiting vacuum of 1.0×10-6Pa within 30 minutes in the vacuum chamber of about 0.23m3.The amorphous Al-doped Si C(Si C-Al) coatings were deposited by RF magnetron co-sputtering of Si C and Al targets on Ti-alloy substrate. The influence of the experimental parameters, including the Al-doping, the Al-buffer layer and the counterpart materials, on the surface tribological properties and interfacial adhesion was evaluated. The results show that the Al-doping strongly affects the mechanical properties of Si C-Al coatings. For example, as Al-content increased, the wear-resistance slowly increased and the friction coefficient changed in a decrease-increase mode, being minimized at an Al-content of 0.97% with the lowest friction coefficient of 0.08. Its friction coefficient against Si C or Al2O3 ceramics is lower than that against stainless steel, being the lowest against SUJ2 steel(in 0.04~0.07 range). The Si C-Al coatings could be able to sustain over 34000 cycles in fatigue-test when the Al-buffer layer is 2 μm thick or more, indicating a heightened interfacial adhesion. Moreover, abrasive wear dominated and no film peeling-off occurred during the process.