利用CO2激光在Q235低碳钢表面激光熔覆制备Ni60合金。分别用扫描电镜、能谱分析、显微硬度计对熔覆层的微观组织、成分分布、显微硬度进行了测定与分析。结果表明,激光熔覆Ni60涂层组织为典型的快速凝固组织。熔覆层底部为垂直于界面生长的胞状结构,中部为树枝状结构且晶粒生长具有单一方向性,顶部也为枝状结构,其晶粒生长呈多向性。枝晶间存在着大量的共晶化合物,黑色区域内含有大量的合金渗碳体等金属间化合物。通过固溶强化、弥散强化、硬质相强化以及细晶强化作用,熔覆层的显微硬度明显高于基材,达到了强化表面的目的。

Ni60 alloy coatings are prepared on the soft steel (Q235) surface by using a CO2 laser. Cross-section microstructure characteristics of the coating are studied by using scanning electronic microscope,energy spectrum,and micro-hardness analysis. The results show that the microstructure of Ni60 coating by laser cladding is typical rapid solidification structure. The morphology at the bottom of the cladding layer is a cell structure,whose growth is perpendicular to the interface of cladding and substrate. The morphology at the central and top zones of the layer is dendritic structure. The crystal grain of central zone grows with a single direction,but that of the surface layer grows with random direction. There are a large number of eutectic compounds at the middle of the dendrite. The black area contains a large number of inter-metallic compounds,such as alloy cementite. With the effects of solid solution strengthening,dispersion strengthening,hard phase strengthening,and fine grain strengthening,the hardness of the cladding layer is obviously greater than that of the substrate,which achieves the goal of hardening surface.