Surface reactivity during a hot isostatic pressing treatment of Ni-based superalloy René 77 specimens manufactured by laser powder bed fusion and metal inject molding

Abstract

Additive manufactured alloys are generally affected by porosity. To solve this issue, Hot Isostatic Pressing (HIP) is a mandatory step. This work focuses on the reactivity of Ni-based superalloy René 77 during HIP at 1200 °C, in argon atmosphere. René 77 is chromia-forming in air at this temperature, but during HIP treatment, it formed α-Al2O3, Al-Ti mixed oxides and TiX (X= nitrogen/oxygen/carbon). The relative quantities of these phases depend on the specimen position inside the furnace, suggesting a gradient of impurity partial pressures. By combining experiments with thermodynamic calculations, this work contributes to a better understanding of HIP processes and suggests ways of improving them.