针对激光熔覆再制造镍基自熔性合金(NiCrBSi)涂层的裂纹问题, 本文提出预热加保温激光熔覆复合工艺技术成功在45钢上制备无裂纹的Ni60A合金涂层。SEM (Scanning Electron Microscope)观察发现Ni60A涂层显微组织主要是树枝状固溶体和晶间网状共晶硬质相, 结合EDS(Energy Dispersive Spectroscopy)和XRD(X-Ray Diffractometer)分析表明熔覆层中树枝状固溶体为γ(Ni), 携带少量Cr和Si, 并富含Fe, 晶间共晶硬质相主要为Ni3B、M23C6(M=Fe, Ni, Cr)以及M7C3, 含有少量CrB硼化物。熔池冷却速度的降低使得晶间共晶硬质相(M23C6、M7C3)减少, 韧性相γ(Ni)增加, 同时熔覆产生金属化合物FeNi3, 熔覆层的韧性得以增强。当预热温度达到300 ℃, 获得无裂纹的Ni60A合金涂层。

The inherent problems associated with laser cladding remanufacturing process using NiCrBSi alloy powder is the formation of crack. Ni60A alloy coatings manufactured by laser hybrid process parameters cladding on 45 steel were investigated. A considerable amount of network eutectics locate in a large number of intergranular positions of the primary matrix under SEM (Scanning Electron Microscope).The results of EDS (Energy Dispersive Spectroscopy) and XRD (X-Ray Diffractometer) find that the coating has homogenous and fine microstructure consisting of γ (Ni) solid solution, a considerable amount of network Ni3B, M23C6 (M=Fe, Ni, Cr) and M7C3 eutectics, with boride ceramic phase CrB uniformly distributing in interdendritic eutectics. With the decreasing of molten pool cooling rate, the intergranular eutectic hard phase (M23C6, M7C3) decreases, and the tough phase γ (Ni) increases, meanwhile, the metal compound FeNi3 is formed during the cladding process, thereby the toughness of the cladding layer is enhanced. The crack is eliminated when preheating temperature is up to 300 ℃.