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The self lubricating wear-resistant coatings were prepared on the surface of 304 stainless steel successfully using laser cladding synchronous powder feeding method, the ratio of cladding powder was pure Co, Co-2%Ti3SiC2(mass fraction, the same below) and Co-8%Ti3SiC2. The microstructure of the cladding coating was characterized by scanning electron microscope(SEM), energy spectrum analyzer(EDS) and X-ray diffractometer(XRD). The tribological performance and related mechanisms of 304 substrate and coatings at RT/600℃ were systematically investigated. The results show that the average microhardness of the N1, N2 and N3 coatings are 285.7HV0.5, 356.3HV0.5 and 463.8HV0.5, which are all much higher than that of the matrix(240.3HV0.5). Co-Ti3SiC2 composite coatings are composed of continuous matrix γ-Co solid solution, hard phase (Fe2C, Cr7C3 and TiC) and lubricating phase Ti3SiC2. At room temperature, the friction coefficients of the matrix and the N1, N2 and N3 coatings are 0.56, 0.62, 0.68 and 0.42, the wear rates of the N1, N2, N3 coatings are 9.15×10-5, 7.81×10-5, 4.66×10-5 mm3/(N·m), which are lower than that of the matrix (66.42×10-5 mm3/(N·m)); at high temperature, the friction coefficients of the matrix and the N1, N2 and N3 coatings are 0.66, 0.54, 0.52 and 0.46, the wear rates of the N1, N2, N3 coatings are 37.79×10-5, 35.6×10-5, 18.83×10-5 mm3/(N·m), which are lower than that of the matrix (41.3×10-5 mm3/(N·m)).At room temperature and 600℃, compared with the 304 stainless substrate, the coatings have the obvious higher microhardness, and the Co-8%Ti3SiC2 coating exhibits the best self-lubricating wear resistance.

304 stainless steel has poor tribological properties at medium and high temperatures, severely limiting its application to the important frictional motion auxiliary parts. In order to improve the tribological properties of 304 stainless steel,Ni60 powder was used as toughening phase,WS2 acted as precursor for synthetic lubricating phase,TiC used as high-hardness and wear-resistant phase,and high-energy laser beam was used to in-situ synthesize a self-lubricating and anti-wear composite coating on its surface. The phase compositions, microstructure,microhardness and surface topogr-aphies of the coating and substrate were characterized by XRD,SEM,microhardness tester,friction and wear tester and the probe-type surface profilometer, and the tribological properties as well as the corresponding wear mechanisms of the coating and substrate at 20,300,600,800 ℃ were systematically studied. Results indicate that the coating is mainly composed of Cr0.19Fe0.7Ni0.11,Ti2SC,Fe2C,Cr7C3,CrS and WS2. Although the average microhardness of the coating (302.0HV0.5) is slightly higher than that of the substrate (257.2HV0.5), the hardness of the upper region of the coating (425.4HV0.5) is about 1.65 times that of the substrate. The friction coefficients and wear rates of coating are lower than that of the substrate at all the isothermal tribological experiments. The coating possesses the best lubrication effect at 300 ℃ with friction coefficient of 0.3031, and the best wear resistance at 600 ℃ with a wear rate of 9.699×10-5 mm3·N-1·m-1.

In order to improve the high temperature tribological properties of Ti6Al4V alloy, multi-phase hybrid metal matrix high-temperature self-lubricating anti-wear composite coating was in-situ synthesized by laser clad with the powder precursor of Ni60-16.8%TiC-23.2%WS2(mass fraction, the same below). The microstructure, phase composition and tribological properties as well as the corresponding wear mechanisms of the composite coating at 20, 300, 600, 800℃ were analyzed systematically. The results show that the microhardness of the composite coating (701.88HV0.5) is about two-fold of the substrate (350HV0.5). Due to the synergetic effect of the in-situ synthesized solid lubricants Ti2SC/TiS/NiS/TiO/TiO2/NiCr2O4/Cr2O3 and hard phases (W,Ti)C1-x/TiC/Cr7C3, both the wear resistant and friction reducing capabilities of the composite coating are better than that of the substrate. With the increase of temperature, the friction coefficient and wear rates of the composite coating and the substrate all exhibit decreasing trend, i.e., the friction coefficient of the composite coating and substrate are 0.32, 0.43 and wear rates are 1.80×10-4, 2.92×10-5mm/Nm at 800℃, respectively. The main wear mechanisms of substrate are mainly plastic deformation and delamination as well as oxidation wear, while the composite coating is predominated by the oxidation wear and slight adhesive wear at 800℃.