Wide temperature range tribological performance of laser <i>in-situ</i> synthesized self-lubricating coating on 304 stainless steel

Abstract

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.

Keywords

• 304 stainless steel
• laser <i>in-situ</i> synthesis
• self-lubricating
• composite coating
• tribological performance