High-Temperature Tensile Properties of Hastelloy X Produced by Laser Powder Bed Fusion with Different Heat Treatments

Abstract

High temperature gradient and rapid solidification rate in the laser powder bed fusion (LPBF) process could result in the presence of columnar grains, which could cause poor high temperature tensile properties in the as-built LPBF Hastelloy X (HX) alloys. Heat treatment could effectively transform columnar grain into the equiaxed grain. However, carbides also are precipitated during heat treatment, which could lead to the reduction in ductility. In this study, we aimed to investigate the effect of carbide morphology and distribution on high-temperature tensile properties of LPBF HX alloys by using different heat treatment methods (the same dwell temperature, different cooling methods). The carbide morphology and distribution after furnace cooling, air cooling, and water quenching were characterized respectively, and were correlated with the high-temperature tensile properties. Scanning electron microscope (SEM) images for the fracture surface and cross-sectional area analysis found that the high-temperature tensile properties, especially the ductility, were affected by the carbide morphologies along grain boundaries.