Promotion of compact coprecipitates by hot isostatic pressing in GH4061 prepared by laser powder bed fusion

Porosities, inevitable in laser powder bed fusion (LPBF) process, seriously degrade the mechanical performance of the manufactured components. The present study explores the effect of hot isostatic pressing (HIP) on the microstructure and mechanical properties of LPBF fabricated nickel-base alloy GH4061. Microstructural analysis shows that high temperature and isostatic pressure during HIP process eliminate porosities completely, achieving 100 % density. High amount of cuboidal coprecipitates, with the γ′ phase at the center and its six faces coated by the γ'' phase, are formed in the HIP treated sample. These compact cuboidal coprecipitates exhibit high thermal stability and remain small size after double-step aging, which is related to the barrier effect of γ'' shell. The LPBF fabricated sample after HIP and double-aging treatment has tensile strength of 1304 MPa and an elongation of 27.8 % at room temperature, surpassing traditionally forged samples. These findings indicate that by eliminating pores through HIP and controlling precipitate morphology via heat treatment, LPBF manufactured samples can achieve mechanical performance superior to traditionally forged ones.