Study Of W-doped Diamond-like Carbon Film And Its Application On High Speed Steel

In this study, W-doped diamond-like carbon(DLC) films were deposited on the high speed steel by unbalanced magnetron sputtering technology. The effect of various W target power as well as substrate nitriding and Cr interlayer on the structure and properties of DLC film were studied. Meanwhile, factors of different friction pairs, humidity and load were applied on the friction experiments of W-DLC film to investigate their influence. X-Ray Diffraction(XRD), Raman spectra, profiler, nano-indentation and scratch tester were applied to systematically study the structure, roughness and basic mechanical properties of the DLC films. Friction and wear tester, Scanning Electron Microscope(SEM) and Energy Dispersive Spectrometer(EDS) were used to study the friction and wear behavior of W-doped.DLC film.The research results of structure and performance of films deposited under W target power of 0kW, 0.1kW and 0.3kW showed that, WC was formed when W doping into the DLC film. The structure of WC/amorphous carbon effectively improved the micro hardness and adhesion strength, at the same time, decrease the friction coefficient and wear rate of the film. Especially, the film deposited under W target power of 0.1 kW possessed the optimum performance.After appropriate ion nitriding process of the high speed steel, CrN phase with high hardness was formed in the surface of the substrate, which changed the nucleation of DLC film and increased the deposition efficiency. The formation of CrN phase promoted the formation of C-N and C-C covalent bonding in the DLC film, meanwhile, ion nitriding process pulled the surface of the substrate into compression and decrease its hardness gap with DLC film. Thus, the adhesion between substrate and film was dramatically improved after nitriding of the substrate. While, the hardness of the DLC film was reduced after substrate nitrding because of the graphitization of C in the film. The result indicated that ion nitriding pretreatment of substrate played a more significant role on the improvement of the adhesion of DLC film than the conventional Cr interlayer.When grinding with various materials, the friction and wear mechanism of the four groups of film differed, which including adhesive wear, abrasive wear and tear, and some friction surface fatigue and oxidation. Simultaneously, with the hardness of friction pair increasing, the friction coefficient of the W-DLC film gradually reduced and the wear rate also showed a general trend of decrease. Under the humidity of 30% and 60%, the friction coefficient went up first then went down with the load raising from 10 N to 40 N and achieve the maximum value at 30 N. While the wear rate of the film kept increasing with the increase of load, and the wear rates of 60% humidity were found to be higher than those of 30% humidity. Raman spectra of the debris demonstrated the graphitization of film after friction, but load and humidity did not affect the structure of debris that much.