Stress-rupture Properties of Hastelloy X Alloy by Selective Laser Melting

In this study, fracture and microstructure analysis were conducted on Hastelloy X alloy formed by selective laser melting(SLM) after high-temperature stress-rupture testing to research the stress-rupture fracture modes and the main factors of the stress-rupture properties. In addition, the microstructure evolution during selective laser melting forming and post-treatment were tracked. The results indicate that the stress-rupture fracture mode of Hastelloy X alloy by selective laser melting is micro-pore aggregation fracture with the intercrystalline dimples. The morphology and amount of carbides, as well as the morphology and orientation of grains, are the main factors that affect the stress-rupture properties of Hastelloy X alloy. In the cooling stage of heat-treatment and hot iso-static pressing, film-like carbides and granular carbides with larger size substantially precipitate along the grain boundaries, reducing the stress-rupture properties. It is suggested that the cooling rate of post-treatment should be adjusted and the alloy should cool rapidly at the temperature near the precipitation peak of carbides to control the morphology and amount of carbides and improve the stress-rupture properties.