Inconel X-750 is a precipitation-hardenable nickel-chromium alloy with the addition of aluminum and titanium. It is known for its high strength at elevated temperatures up to about 815°C (1,500°F), as well as excellent creep-rupture properties and good oxidation and corrosion resistance. The alloy is age-hardened by the formation of gamma prime (Ni3(Al,Ti)) precipitates.

The nominal chemical composition is: nickel 70.0 percent minimum, chromium 14.0 to 17.0 percent, iron 5.0 to 9.0 percent, titanium 2.25 to 2.75 percent, aluminum 0.40 to 1.00 percent, niobium (plus tantalum) 0.70 to 1.20 percent, and smaller amounts of carbon, manganese, silicon, and sulfur.

Key mechanical properties (typical, aged condition):

● Tensile strength: 1,100 to 1,300 MPa

● Yield strength (0.2% offset): 700 to 900 MPa

● Elongation: 15 to 25 percent

● Hardness: 30 to 40 HRC

● Density: 8.28 g/cm³

Inconel X-750 offers good relaxation resistance, excellent fatigue strength at high temperatures, and resistance to oxidation and corrosion in high-temperature environments. It is also used at cryogenic temperatures due to its retained ductility. The alloy is weldable, but precipitation hardening after welding may be required to restore full strength.

Common standards: AMS 5698/5699 (wire), AMS 5582 (sheet, strip), AMS 5667/5668 (bar, forgings), ASTM B637 (bar).

Typical applications include:

● Gas turbine engines: blades, vanes, seals, and combustion chamber components.

● Nuclear reactors: core components, springs, and fasteners (good resistance to radiation damage).

● Rocket engines: thrust chambers and turbo pump parts.

● Heat treating fixtures: baskets, trays, and furnace hardware.

● Springs and fasteners for high-temperature service (e.g., jet engine bolts).

Comparison with other Inconel alloys: Inconel X-750 has higher high-temperature strength than Inconel 600 or 625 due to precipitation hardening. Compared to Inconel 718, X-750 has slightly lower strength at intermediate temperatures (around 650°C) but better relaxation resistance and is often used for springs and bolts. For maximum strength at 700°C, Inconel 718 is more common; for even higher temperatures (above 800°C), alloys like Waspaloy or René 41 are preferred.

Selection guidance: Choose Inconel X-750 for high-temperature springs, fasteners, and gas turbine components requiring good creep resistance and relaxation resistance up to about 815°C. For welded structures or where higher strength at 650°C is needed, Inconel 718 may be more suitable. For lower strength but better corrosion resistance, Inconel 625 is an alternative.