Hastelloy X is a nickel-chromium-iron-molybdenum alloy (approximately 47 percent nickel, 22 percent chromium, 18 percent iron, 9 percent molybdenum) with good high-temperature strength and excellent oxidation resistance up to about 1,200°C (2,200°F). It is solid-solution strengthened and is not precipitation hardenable.

The nominal chemical composition is: nickel 47.0–52.0 percent, chromium 20.5–23.0 percent, iron 17.0–20.0 percent, molybdenum 8.0–10.0 percent, cobalt up to 1.5 percent, tungsten up to 1.0 percent, and smaller amounts of carbon, manganese, and silicon.

Key mechanical properties (typical, annealed condition at room temperature):

● Tensile strength: 690–790 MPa

● Yield strength (0.2% offset): 310–380 MPa

● Elongation: 30–45 percent

● Density: 8.22 g/cm³

At high temperatures (e.g., 815°C / 1,500°F), Hastelloy X retains good strength with a tensile strength of approximately 350 MPa and yield strength of 240 MPa.

Hastelloy X offers outstanding oxidation resistance, carburization resistance, and good creep-rupture strength at elevated temperatures. It also resists nitriding and has good fabricability (welding, forming). The alloy is not recommended for strongly reducing environments or for prolonged exposure in the temperature range where sigma phase may form (650–900°C) unless stress levels are low.

Common standards: ASTM B435 (plate, sheet, strip), B572 (rod, bar), B622 (seamless pipe and tube), B619 (welded pipe), ASME SB-435, SB-572, SB-622, and AMS 5536 (sheet), AMS 5754 (bar).

Typical applications include:

● Gas turbine engines: combustion chamber liners, transition ducts, burner cans, and afterburner components.

● Industrial heating: furnace muffles, radiant tubes, thermocouple sheaths, and retorts.

● Petrochemical processing: catalyst grid supports and furnace hardware.

● Aerospace: tailpipes and exhaust systems.

Comparison with other high-temperature alloys: Inconel 617 has higher creep strength above 900°C, while Inconel 625 offers better aqueous corrosion resistance. Hastelloy X is often chosen for its excellent combination of oxidation resistance, fabricability, and moderate cost. For maximum high-temperature strength, alloys like Haynes 230 or 188 may be preferred.

Selection guidance: Choose Hastelloy X for high-temperature components (up to 1,200°C) requiring oxidation and carburization resistance, especially in gas turbine and industrial furnace applications. For strongly reducing or corrosive chemical service at lower temperatures, a C-series Hastelloy (e.g., C-276) is more suitable.