Hastelloy X is an alloy of nickel, chromium, and iron. It has excellent high-temperature oxidation and corrosion resistance properties and good strength at elevated temperatures. The composition of Hastelloy X consists of 57% Nickel (Ni), 20% Chromium (Cr), 17.5–20% Cobalt (Co), 1–3% Molybdenum (Mo), 0.2–1% Tungsten (W), up to 0.2 % Tantalum (Ta). This alloy resists stress rupture cracking in high-temperature environments and can survive operating conditions up to 2100°F or 1150°C. In addition, this formable material performs well in applications requiring fabricability at cryogenic temperatures down to –423°F or –253°C.

Hastelloy X is an iron-based superalloy developed to overcome nickel-based alloys' limitations. It exhibits excellent resistance to stress corrosion cracking, oxidation and scaling at high temperatures and superior strength and flexibility compared to other alloys in its class. Hastelloy X is often used in chemical processing because it can resist chloride-ion pitting and stress corrosion cracking. In addition, it has been used for aircraft components such as blades, hubs and disc brakes due to its strength at extreme temperatures and fatigue resistance. Its nonmagnetic properties make it ideal for producing hypersonic propulsion systems such as rocket nozzle assemblies or jet engine turbine blades.