High Pressure Heat Treatment for L-PBF Hastelloy X

Abstract

Abstract Hastelloy X is used in turbomachinery and petrochemical applications as it is designed for excellent oxidation and stress corrosion cracking resistance, strength, and stress rupture behavior. This alloy is now being printed via powder bed fusion processes as many industries have developed interests in the benefits additive manufacturing (AM) offers. However as-printed Hastelloy X suffers from material defect formation such as hot cracking. Hot isostatic pressing (HIP) is often applied to improve performance and reliability. Although the conventional HIP process has been shown to eliminate defects, the equipment is unable to cool at desired rates allowing the formation of excessive carbide precipitation, negatively influencing corrosion resistance and toughness. In turn the product is solution treated at a similar temperature while applying rapid gas cooling for performance requirements. With use of uniform rapid cooling available in modern HIP equipment, a high-pressure heat treatment can be applied offering the ability to perform both HIP and heat treatment in one piece of equipment. Microstructure and tensile properties are evaluated and compared to the conventional processing routes. The results demonstrate that the novel high pressure heat treatment approach offers a processing route that is equivalent to or better than conventional methods.