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. © 2012, Northwest Institute for Nonferrous Metal Research.