Annealing of Additively Manufactured Inconel 625

Abstract

The objective of this work is to study the effect of heat treatment on Inconel-625 fabricated by using selective laser melting. Annealing is performed to relieve stresses, improve the ductility, and toughness of Inconel-625. As-built Inconel-625 samples are annealed at temperatures ranging from 700 to 1200 °C. A numerical approach is developed to capture the phase transformation during annealing. The microstructure of the as-built and annealed samples are compared and their hardness is determined experimentally. The as-built microstructure consists of austenite phase without any precipitates. The heat treatment at lower temperatures leads to the formation of orthorhombic Ni3Nb which dissolves at higher temperatures. Meanwhile metal carbide precipitates are observed upon heat treatment at higher temperatures. The heat treatment at low temperatures leads to the formation of intermetallic phases thereby increasing hardness. The intermetallic compounds dissolve at higher temperatures and grain size increases leading to reduced hardness.