Microstructure characteristics and failure mechanisms of hybrid manufacturing of FGH96 and IC10 bimetal component using laser directed energy deposition

Hybrid manufacturing technology combines the cost advantage of traditional manufacturing with the flexibility benefit of additive manufacturing, thus providing an effective solution for creating gradient components. In this work, we deposit IC10 alloy powders on the FGH96 hot isostatic pressing substrates to prepare nickel-based gradient materials. A detailed analysis of the microstructural evolution in different regions is provided. The influence of thermal cycles on the heat-affected zone (HAZ) causes the γ′ phase to transform from a multimodal structure formed by hot isostatic pressing to a uniform spherical shape. The grain morphology changes from the ultrafine equiaxed grains of the substrate to fine equiaxed grains in the HAZ, then transforms into fine columnar grains in the gradient region, and finally changes to coarse columnar grains in the deposited zone. Moreover, the influence of grain orientation on the ability of epitaxial growth is investigated, and a grain orientation-dependent growth model is developed to predict the growth direction of columnar grains in the deposited layer. Such a non-uniform microstructure results in mechanical performance, including hardness and tensile strength, with distinctive heterogeneity along the building direction. The hybrid manufactured sample with higher yield strength than the pure alloys was primarily influenced by factors such as grain sizes, the sizes and distributions of the γ′ phases, as well as dislocation densities. However, due to the liquation crack in HAZ, the tensile elongation of the hybrid manufactured sample is lower than the pure alloy.