Abstract: Solid lubricating layers of sulfurized layer and phosphate layer were prepared on the surface of gray cast iron by low temperature ion sulfurization technology and chemical conversion technology, respectively. SEM-EDS, XRD, nano-indentation apparatus and X-ray stress analyzer were used to analyze the component elements, microstructure, thickness, hardness, residual stress and wear scar morphologies of the solid lubricating layers. The anti-friction and wear properties of the gray cast iron substrate and surface solid lubrication layer were studied by friction and wear test. The wear volume after friction and wear test was analyzed by using three-dimensional white light interferometer. The results show that both the phosphate layer and the porous structure of the sulfurized layer on the surface of gray cast iron have the characteristics of oil storage lubrication, while the surface hardness and residual stress of the sulfurized layer are higher than that of the phosphate layer. The sulfurized layer is detected to be a covalent bond compound FeS with antifriction and lubrication effect, which is formed when the active sulfur atoms infiltrate into the matrix, there is also a dynamic equilibrium process of active sulfur atoms transfer and recombination during the grinding process of gray cast iron substrate and sulfurized layer. Therefore, compared with the phosphate layer under the same friction conditions, the friction coefficient of the sulfurized layer is reduced by 23.5% and the wear rate is decreased by 31.6%, i.e., the anti-friction, wear-resisting and wear-resisting properties of sulfurized layer is better than that of phosphate layer, the COP of compressor parts after sulfurizing treatment is significantly improved.

Key words: gray cast iron, phosphorzation, low temperature ion sulfurization, residual stress, friction and wear