Research status of surface modification of gray cast iron

Since the 1990s, researchers have carried out a lot of research on the surface modification of gray cast iron, among which the research on laser melting of gray cast iron mainly focuses on the microstructure analysis.

Sun et al. Analyzed the metallographic structure of the melting layer after laser melting treatment on the surface of gray cast iron. The results showed that the fine cementite dendrite structure was formed in the melting layer of gray cast iron, the graphite phase in the melting layer disappeared, and the wear resistance of the melting layer was three times higher than that of the original sample.

Liu et al. Carried out laser melting treatment on the surface of gray cast iron, analyzed the size of the melting layer under different laser parameters, and measured that the hardness of the melting layer of gray cast iron was 700 ~ 800 hv0 Between 2. At the same time, the changes of the hardness of the fused layer under different laser lap rate were studied. Zhang Qingmao and others carried out a rapid wear test on the surface of gray cast iron after laser melting. The experimental results show that the wear depth of the sample after laser melting is 1.35 μ m. The friction coefficient varies from 0.072 to 0.082.

Cheng Xiu carried out friction and wear experiments and friction fatigue experiments on gray cast iron and nodular cast iron after laser melting respectively. The experimental results show that the melting layer of nodular cast iron is larger than that of gray cast iron. Under the same laser power, the crack sensitivity of heat affected zone of gray cast iron is greater than that of nodular cast iron, and the shape of flake graphite is easy to cause cracks in heat affected zone. In recent years, Laser shock technology is mainly used to solve the problem of cladding layer cracking after laser cladding. Yan et al. Carried out laser shock treatment on Fe314 alloy cladding layer. After laser shock, the residual tensile stress of cladding layer is transformed into residual compressive stress, and large plastic deformation occurs in cladding layer.

After Jingxiang laser cladding 316L stainless steel, it is found that due to the large residual tensile stress in the cladding layer, cracks are easy to occur in the cladding layer. The laser impact can transform the residual tensile stress in the cladding layer into residual compressive stress, refine the stainless steel grains in the cladding layer, make the microstructure of the cladding layer more dense, and effectively improve the microstructure defects in the cladding layer.

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