TC4合金表面激光熔覆B4C及B4C＋Ti粉末涂层的微观组织

Microstructure of Laser Cladding Coating with Pre-Placed B4C and B4C+Ti Powders on TC4 Substrate

摘要:

利用XRD，SEM和EDS分析手段对B4C和B4C＋10％Ti（质量分数，下同）激光熔覆层的微观组织进行了分析。结果表明，TC4合金表面B4C与B4C＋10％Ti激光熔覆层的组成相基本相同，均由TiC1-x，TiB，TiB2和Ti相组成，说明在TC4合金表面熔覆过程中有一部分Ti进入熔覆层并与B4C发生化学反应原位生成了TiB，TiB2和TiC1-x相。TiC1-x相以树枝状相形式存在，TiB2相以粗大须状相形式存在，TiB相以细小须状相形式存在。熔覆层与基底结合良好，没有发现裂纹与孔洞。基底热影响区呈淬火组织形貌，为典型的针状马氏体组织特征。与B4C激光熔覆层相比，B4C＋10％Ti激光熔覆层的组织细小，TiB相含量增多，TiB2相含量减少。

Abstract:

The microstructure of the laser cladding coating with pre-placed B4C and B4C+Ti powders on TC4 substrate was analyzed using XRD, SEM and EDS. The results showed that both the coatings consisted of TiB2, TiB, TiC1-x and Ti phases. Some of Ti in the substrate was melted and mixed into the laser melting pool and reacted with B4C in-situ producing TiB, TiB2 and TiC1-x. The in-situ produced TiC1-x shows morphology of dendrite. The in-situ produced TiB2 shows morphology of whisker with larger size. The in-situ produced TiB shows morphology of whisker with smaller size. The bonding between the coating and TC4 alloy substrate was perfect. No crack and void were found at the interface. The heat-affected zone in the Ti substrate exhibited typical martensite morphology of quenched microstructure. Compared with B4C cladding coating, the B4C+10wt%Ti cladding coating had a finer microstructure and higher content of TiB phase and lower content of the TiB2 phase.