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高功率CO_2激光送粉熔覆Stellite和NiCrSiB合金对比实验表明:NiCrSiB合金激光熔覆具有很大的裂纹倾向,NiCrSiB+50％Ni不出现裂纹,前者微观组织特征为少量的韧性相和大量不规则杂乱分布的粗大硬质相,后者为典型枝晶结构。Stellite 6合金激光熔覆不出现裂纹,Stellite 6+18％以上WC出现裂纹,前者微观组织特征为先共晶枝晶和枝晶间共晶,后者枝晶间共晶增多、共晶内碳化物析出物增多并出现多种复杂形状的碳化物无规沉淀析出。激光熔覆层裂纹形成的根本原因是由于熔覆过程产生的很大拉应力,裂纹形成的主导原因是由于激光熔覆层本身的韧性太低而脆性太大,难以承受大的拉应力。降低裂纹倾向的思路是改变熔覆层内强化相的形态,使其以颗粒形式均匀弥散地析出,同时使强化相颗粒由底部至表面呈梯度分布。
High power CO_2 laser powder cladding Stellite and NiCrSiB alloy contrast experiments showed that: NiCrSiB alloy laser cladding has a great tendency to crack, NiCrSiB + 50% Ni is not cracked, the former microstructure is characterized by a small amount of ductile phase and a large number of irregular Scattered distribution of coarse hard phase, which is a typical dendritic structure. Stellite 6 alloy laser cladding does not appear cracks, Stellite 6 + 18% above WC cracks, the former microstructure characteristics of the first eutectic dendrite and interdendritic eutectic, latter dendrite eutectic increased eutectic carbide precipitation An increase in the number of substances and the occurrence of a variety of complex shapes of carbide precipitated randomly. The fundamental reason for the formation of laser cladding cracks is due to the large tensile stress caused by the cladding. The main reason for the crack formation is that the laser cladding itself is too tough and too brittle to withstand large tensile stress. The idea of reducing the crack tendency is to change the morphology of the reinforcing phase in the cladding layer so that it is uniformly and dispersedly precipitated in the form of particles and at the same time, the reinforcing phase particles are distributed gradiently from the bottom to the surface.