Effect of laser energy density on the microstructure, mechanical properties, and deformation of Inconel 718 samples fabricated by selective laser melting

Abstract

Inconel 718 samples were fabricated by selective laser melting (SLM). The effects of line laser energy densities in the range 0.1–0.3 J/mm on the microstructure, mechanical properties, and deformation of these samples were investigated. The fewest pores and best mechanical properties were realized at 0.2 J/mm with a yield strength of 775 MPa, ultimate tensile strength of 1055 MPa, and elongation of 29.5%. Fine dimples were uniformly distributed on the fracture surface under 0.2 J/mm. An Electron Backscatter Diffraction (EBSD) test revealed a mixture of fine columnar and equiaxed grains that promote strength while maintaining high plasticity. The prisms cut from these samples bent outwards, indicating great residual stresses in the samples. Their deformation increased with increasing laser energy density. Therefore, stress release treatment is necessary for SLM parts.