A351 HK40

HK40 is a high-temperature austenitic stainless steel casting alloy designated under ASTM A351/A351M. It is primarily used for components subjected to prolonged exposure to elevated temperatures, such as reformer tubes, heat exchanger components, and furnace parts. HK40 is composed of approximately 25% chromium and 20% nickel, providing excellent resistance to oxidation, carburization, and other forms of high-temperature degradation. This alloy is valued for its strength retention and structural stability in thermal environments exceeding 1000 °F (540 °C), making it well-suited for applications in petrochemical processing, heat treatment equipment, and industrial furnaces. Its performance under thermal cycling and resistance to creep make HK40 a standard material for cast components in severe service conditions.