Effect of heat treatment on microstructure, corrosion resistance, and interfacial characteristics of Inconel 625 laser cladding layer

In this study, the changes in the microstructures and properties of an Inconel 625 cladding layer and its heat-affected zone (HAZ) upon heat treatment at 650 °C for 1 h were investigated. The interface characteristics were studied by removing the substrate through chemical and physical stripping. The results indicate that heat treatment can reduce the enrichment of Mo and Nb in the interdendritic region of the cladding layer, thereby distributing them more evenly. After heat treatment, the HAZ microstructure changed noticeably. Further, the martensite decomposed, ferrites formed, grains grew, and the microhardness decreased observably. The corrosion resistance of the cladding layer after heat treatment increased because the passivation film became more difficult to destroy. The interface maintained the microstructural characteristics of both the substrate and cladding layer. A “dendrite skeleton” was distributed in the grain of the sample before heat treatment; however, the dendrite characteristics became less prominent because of diffusion after heat treatment. Thus, the interface mainly retained the characteristics of the substrate. The bonding interface fractures showed a mixed fracture mode regardless of the heat treatment; however, the dimple morphology of the heat-treated sample differed substantially from that of the non-heat-treated sample, and no dendritic characteristics were observed after heat treatment.