High Pressure Heat Treatment for L-PBF Hastelloy X

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 AM offers. However as-printed Hastelloy X suffers from material defect formation such as hot cracking. A HIP processing treatment 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 solution treatment in one piece of equipment. Microstructure, hardness, tensile properties, and corrosion resistance is evaluated and compared to the conventional processing route of performing a separate HIP and solution treatment. The results demonstrate that HPHT offers a processing route that is equivalent to or better than conventional methods.