| Light metals (Mg, Al, Ti) are widely used in many fields such as aviation and spaceflight, weapon equipment and biomedicine et al, however their friction and wear properties need to be improved. Silicon carbon (SiC) film and carbon based (diamond-like carbon-DLC, carbon nitride-CNx) film are known to have low friction coefficient and high wear-resistance. For this paper, the friction and wear properties (using a ball-on-disc type friction and wear tester, and silicon nitride balls) of the thin films (SiC, SiC/DLC, SiC/CNx, et al) deposited (using magnetron sputtering technology at room temperature) on conventional coarse grained magnesium alloy (AZ91D), conventional coarse grained aluminum alloy (2024), nanocrystalline aluminum alloy (2024), conventional coarse grained titanium, conventional coarse grained titanium alloy (Ti-6Al-4V) and nanocrystalline titanium were investigated.Firstly, the friction and wear properties of coarse grained magnesium alloy, coarse grained magnesium alloy/films (SiC, SiC/DLC, SiC/CNx) are studied under room temperature and dry friction conditions. The results show that relative to the magnesium alloy, the magnesium alloy/SiC/DLC and the magnesium alloy/SiC/CNx both exhibit a lower friction coefficient and a much higher and impressive wear-resistance.Secondly, the friction and wear properties of coarse grain aluminum alloy, coarse grain aluminum alloy/films (SiC, SiC/DLC), nanocrystalline aluminum alloy, and nanocrystalline aluminum alloy/Ti/SiC were studied. The results show that relative to the coarse grained aluminum alloy and the nanocrystalline aluminum alloy, the coarse grained aluminum alloy/films (SiC, SiC/DLC) and the nanocrystalline aluminum alloy/Ti/SiC can also respectively exhibits a lower frictional coefficient and higher wear-resistance at a small contact load.Thirdly, the friction and wear properties of coarse grained titanium, coarse grained titanium/films (SiC, SiC/DLC, SiC/CNx), coarse grained titanium alloy, coarse grained titanium alloy/films (SiC, SiC/DLC, SiC/CNx), nanocrystalline titanium, and nanocrystalline titanium/films (SiC, SiC/DLC, SiC/CNx) are studied. The results show that the these above substrates/films systems exhibit a much better friction and wear properties than those of the merely substrates, the substrate nanocrystallization improves wear-resistance of film-substrate system at high load considerably, and the friction and wear properties of the nanocrystalline titanium/films systems are superior under simulated body fluid (Kokubo) than under dry friction conditions.Based on above investigation, the extreme importance of substrate chemical activity to wear-resistance of film-substrate systems at high load was found. Relative to the aluminum alloy substrate, the magnesium alloy substrate has a higher activity and therefore the corresponding film-substrate systems exhibit a better wear-resistance. Relative to the coarse grained titanium substrate, the nanocrystalline titanium substrate has a higher activity and therefore the corresponding film-substrate systems also exhibit a better wear-resistance. The underlying mechanisms are believed to be able to be ascribed to the increased substrate-induced crystallization of surface films caused by the high substrate activity, which will lead to an increase in ductility and toughness of films (due to a sliding occurring at interface of amorphous phase and crystalline phase), and an improvement in the elastic modulus match between film and substrate. |
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