中文摘要：

针对镍基高温合金叶片强化与修复的需求,在高温合金K438基体上激光熔覆Inconel 738合金涂层。分析了基体组织及熔覆层中微观缺陷对熔覆层裂纹的影响。结果表明,激光熔覆时大多数裂纹是从基体一侧形成后深入到熔覆层中或产生于层与层之间的搭接区,裂纹沿晶界扩展。沿晶界分布的低熔点共晶物是主要的裂纹源。激光熔覆时,晶界处的γ/γ′低熔点共晶物熔化,形成晶界液膜,冷却时,在残余拉应力的作用下被拉开,形成裂纹,裂纹一旦形成就会沿晶界迅速扩展。

英文摘要：

In view of the strengthening and repair of Ni-base superalloy blades,laser cladding Inconel 738 powder on the substrate of superalloy K438 was carried out.The effects of the substrate microstructure,microscopic defects of the cladding layer on cracks were investigated.The results show that most of the cracks penetrated into the cladding layer have forming from one side of the substrate or the overlapping zone,and extended along the crystal boundary.The eutectic phase with low melting point is the main sources of the cladding cracks.During the laser cladding,the γ/γ′eutectic phase with low melting point can liquefy,and form grain boundary film.While cooled,the eutectic phase can be pulled apart by the residual tensile stress,leading to the formation of crack,which will rapidly expand along the grain boundary as it forms.