Preparation And High-temperature Tribological Properties Of SiC Thin Films

With the rapid development of industrial technology,more and more mechanical parts need to operate at high temperature,so the development of the high-temperature lubrication materials is particularly important.SiC thin film is one of the potential candidates for high-temperature lubrication due to its excellent properties,such as high hardness and elastic modulus,strong oxidation resistance,good thermal stability,high strength at elevated temperature,low thermal expansion coefficient,good thermal shock resistance and so on.This thesis summarizes the research status of SiC thin film used as lubricating materials,and analyzes the advantages and disadvantages of SiC thin film as high-temperature lubricating material.SiC thin films were deposited by magnetron sputtering,and the influence of sputtering powers and substrate bias on the structure and mechanical properties were studied.The high-temperature tribological properties of SiC thin film possessing better mechanical properties were studied and then optimized by introducing C₂H₂in the preparation process.Mainly research achievements were described,as following:(1)The effect of sputtering power on the structure and mechanical properties of SiC thin films was studied.The results show that,as the increasing power from 100W to160W,the energy of sputtering particles increases,the density and the content of Si-C bonding of the film increases,and the I(D)/I(G)ratio decreases.The hardness(H)and elastic modulus(E)show an increasing trend.Then,the effect of bias voltage on structure and mechanical properties of SiC thin film deposited.The results show that when the substrate negative bias from 0V to 100V,the density,content of Si-C bonding and I(D)/I(G)of the film increases.And then the negative bias is further increased to 150V,the film density,content of Si-C bonding,and I(D)/I(G)decreases.With the increase of bias voltage,H and E increased first and then decreased,and the maximum values are 21 GPa and 230 GPa at-100 V,respectively.(2)The high-temperature tribological properties of SiC thin films prepared at the power of 160 W and the bias voltage of-100 V were studied.The results show that the films fail rapidly at room temperature,and the friction coefficient decreases from0.8 at 300 ^oC to 0.54 at 500 ^oC and then increases slightly to 0.57 at 600 ^oC.At 300 ^oC,the wear mechanism is typical abrasive wear.Over 400 ^oC,a transfer film is formed on the surface.It is concluded that the excellent oxidation resistance and mechanical properties of the SiC film,and oxidation films(Fe_xO_yand Si O_x)formed at the lubrication interface play important roles for improving the high-temperature tribological properties of the film.For further optimization of the high-temperature tribological properties of SiC thin film,the carbon-rich SiC thin film were preparated by adding C₂H₂during the preparation process,and its high-temperature tribological properties were studied.The results show that the in-situ friction performed from room temperature to 500 ^oC,the coefficient of friction and wear was the first to increase decrease then increase slightly,and all the average static coefficient of friction film is less than 0.13,wear rate at 10^-7mm³N^-1m^-1orders of magnitude.