激光成形修复K418高温合金的显微组织与开裂行为

研究了激光成形修复航空发动机涡轮叶片用K418高温合金的组织特征与开裂行为。研究发现:K418合金激光修复区组织主要由γ-FeCr0.29Ni0.16C0.06固溶体基体、方形γ′相、枝晶间杆状或骨架状初生MC碳化物和骨架状(γ+MC)共晶组成。激光成形修复所用铸件基体中MC碳化物为TiC,呈块状分布在晶内和晶界;而激光修复区中MC碳化物为(NbTi)C,呈骨架状或杆状分布于枝晶间。从基体、热影响区到修复区,γ′相形貌、尺寸和数量呈现不同特征。修复区裂纹为与液膜有关的结晶裂纹,裂纹沿枝晶晶界扩展。通过试验优化,确定了较佳的激光成形修复K418合金的工艺参数,大大降低了其开裂倾向。

Microstructure and Cracking Behavior of K418 Superalloy by Laser Forming Repairing

The microstructure and cracking behavior of K418 superalloy applied in turbine blade by laser forming repair were investigated. The results indicate that laser repair zone (LRZ) is mainly composed of γ-FeCr0.29Ni0.16C0.06 solid solution matrix, cubic γ′ phase, rod or skeleton shaped primary MC and interdendritic (γ+MC) eutectic. MC carbides of cast substrate zone (CSZ) are blocky TiC distributing in intragranular and intergranular fields, but MC carbides of LRZ are skeleton or rod shaped (NbTi)C. From CSZ, heat affected zone (HAZ) to LRZ, the morphology, size and quantity of γ′ phases are different. The cracks of LRZ are solidification cracks related to the liquid film, and they propagate along interdendritic regions. Better parameters of LFR are achieved, and the tendency to crack of K418 alloy repaired by LFR is reduced greatly.