Effect of stress relief and solubilization heat treatments on laser additive manufactured Inconel 625: microstructure and properties

Abstract

This work assesses the effect of the energy input and the stress relief and solubilization heat treatment on the microstructure and mechanical properties of an Inconel 625 alloy processed by laser additive manufacturing using directed energy deposition. Two processing conditions were used to deliver high productivity with a high energy input (HEI) and another with better geometrical precision using a lower energy input (LEI). The mechanical test samples were built vertically and horizontally aligned with the tensile test direction. The samples were submitted to residual stress relief (SR) and SR + solubilization (S) heat treatments (SR + S). Results showed increased elongation with solubilization heat treatment, while UTS and YS decreased with heat treatment combination, which was linked to the stronger texture developed in HEI condition. Samples built in the vertical direction presented lower YS. The fracture toughness of solubilization heat-treated samples showed higher values, while LEI gave just slightly higher values. Although the microstructural and mechanical features are similar between the HEI and LEI conditions, the first stands out because parts can be fabricated quickly without losing mechanical performance under quasi-static conditions, impact fracture tests, or the production of unwanted phases.