TC4表面激光熔覆TiC和TiC-NiCrBSi涂层的微观组织研究

采用激光熔覆技术在TC4合金表面制备TiC和TiC-NiCrBSi涂层,研究了激光熔覆层的微观组织和硬度。结果表明,在TiC激光熔覆层中,表层(熔覆区)大部分TiC颗粒发生了熔化并以树枝晶形式结晶,底层(稀释区)TiC颗粒向钛合金中溶解并以树枝晶形式沉淀析出。随激光比能的增加,基底钛合金的稀释作用增加,熔覆层的硬度降低。在TiC-NiCrBSi激光熔覆层中,熔覆区中的TiC颗粒向Ni基合金中溶解并以细小的球状颗粒和树枝晶形式沉淀析出,随激光比能的增加,TiC颗粒的溶解程度增加。当TiC颗粒的体积分数超过50%时,TiC颗粒出现偏聚现象。TiC-NiCrBSi激光熔覆层的稀释区是Ni基合金和钛合金的混熔区,呈细小的树枝晶形态。

Microstructure of TiC and TiC-NiCrBSi laser clad layers on Ti-6Al-4V alloy substrate

Laser cladding with TiC and TiC-NiCrBSi po wd ers on Ti-6Al-4V alloy substrate was carried out, and microstructure, as well as microhardness profile, in the laser clad layers was examined. The results showe d that, in the TiC laser clad layer, TiC was melted and solidified to form dendr ites in the clad zone, and dissolved into the melted Ti alloy and precipitated t o form dendrites in the dilution zone. With increasing specific laser energy, th e dilution effect of the substrate of Ti alloy was enhanced and the microhardnes s decreased in both the clad and the dilution zone. In the TiC-NiCrBSi laser cla d layers, TiC particles dissolved into the melted Ni-base alloy in the clad zone . With increasing specific laser energy, the degree of solution of TiC particles was increased. During cooling, fine spherical particles and dendrites of TiC pr ecipitated from the Ni-base alloy. When the TiC volume fraction increased to mor e than 50%, clustering of TiC particles was observed in the clad zone. The clust ering of TiC particles resulted in a decrease in the homogeneity of microstructu re and microhardness distribution in the clad zone. The dilution zone of the TiC -NiCrBSi laser clad layer is a mutually melted region of the Ni-base alloy and s ubstrate of titanium alloy and presents microstructure of dendrites.