Effect of heat processing on microstructures and tensile properties of selective laser melting Hastelloy X alloy

Abstract

The technology of selective laser melting was used to fabricate Hastelloy X samples. The effect of hot isostatic pressing (HIP) and solution treatment on microstructures and tensile properties of Hastelloy X samples was investigated. The results show the as-deposited samples exhibit clear melt pool morphologies, columnar grain with embedded cellular structures and no obvious precipitates are detected. The corresponding tensile properties are characterized by high strength and low ductility. High temperature tensile fracture surface reveals that the as-deposited samples crack along laser scan tracks. After HIP, the microstructures evolved into equiaxed grains, and large amount of precipitates are found to distribute within grain boundaries and grain interiors. Besides, solidification cracks are effectively healed by HIP. In this circumstance, the tensile strength is decreased by about 48% combined with improved ductility up to 59% after high temperature tensile tests. After HIP+solution treatment, the grain size and morphology keep similar with that in HIP processed state, while the amount of precipitates inside grain areas is significantly reduced and an overall sound tensile property is achieved.

Keywords

• selective laser melting
• Hastelloy X
• heat processing
• microstructure
• tensile property