Microstructure and Microhardness of Laser Forming Repaired K418 Superalloy

The microstructure and microhardness of laser forming repaired (LFRed) K418 superalloy were investigated. The results reveal that the LFRed sample can be divided into cast substrate zone (CSZ), heat-affected zone (HAZ) and laser repaired zone (LRZ). The microstructures with different morphology, size and number are composed of γ-FeCr_0.29Ni_0.16C_0.06 matrix phases, γ'-Ni₃Al phases and MC carbides phases. The LFRed sample presents a compact metallurgical bonding between CZS and LRZ. The LRZ presents columnar dendrites which grew epitaxially along the direction of deposition and a consecutive layer structure. There are difference in microhardness because of difference in grains size at the same deposition layer. The average microhardness of CSZ, HZA and LRZ reach 432.4, 499.4 and 490.6 HV, respectively.