High-power laser powder bed fusion of In718 alloy using coarse powders: Defect, microstructure and mechanical property

High-power laser powder bed fusion technology (HP-LPBF) which uses kilowatt-level fiber lasers allows for the use of larger layer thickness in comparison to the conventional laser powder bed fusion technology (LPBF). Therefore, coarse powders with low cost can be utilized to reduce manufacturing costs. In this work, gas atomized coarse powders with D₅₀ of 86.4 μm were used for the HP-LPBF of In718 Ni-base superalloy. For comparison, gas atomized fine powders with D₅₀ of 32.8 μm were also used. The defects, microstructures and mechanical properties of the different as-built samples were studied to reveal the influence of using coarse powders. The results show that the relative density of as-built sample decreases when using coarse powders. The samples made of fine powders possess a typical columnar microstructure, while the samples made of coarse powders exhibit a duplex microstructure, which is composed of columnar grain matrix and equiaxed fine grain agglomerations. Although the defect and microstructure of as-built In718 are sensitive to powder size, the tensile properties of the sample made of coarse powders are comparable to those made of fine powders. The influencing mechanisms of powder size on defect, microstructure and tensile properties were analyzed by considering multiple factors. The results also demonstrate that the tensile properties of the samples made of coarse powders can exceed the standard values of In718 forgings after conducting a proper solution and double aging treatment. Besides, the method to improve the relative density and as-printed mechanical properties when using coarse powders was also proposed. The results of this study help to reduce the material costs of LPBF technology.