Incoloy 800 is a nickel-iron-chromium alloy (approximately 32–35 percent nickel, 19–23 percent chromium, and balance iron). It is designed for high-temperature service, offering good strength and excellent resistance to oxidation, carburization, and sulfidation. The alloy is solid-solution strengthened and is not precipitation hardenable.

The nominal chemical composition is: nickel 30.0 to 35.0 percent, chromium 19.0 to 23.0 percent, iron 39.5 percent minimum, carbon up to 0.10 percent, manganese up to 1.5 percent, silicon up to 1.0 percent, and aluminum + titanium 0.15 to 0.60 percent.

Key mechanical properties (typical, annealed condition):

● Tensile strength: 520 to 690 MPa

● Yield strength (0.2% offset): 210 to 310 MPa

● Elongation: 30 to 45 percent

● Density: 7.94 g/cm³

Incoloy 800 offers good resistance to high-temperature oxidation and scaling up to about 1,100°C (2,000°F). It resists carburization and nitriding in many industrial heating environments. The alloy also provides good creep-rupture strength and retains ductility after long-term high-temperature exposure. In aqueous environments, it has moderate corrosion resistance, generally superior to stainless steels but lower than nickel-based alloys like Inconel 600.

Common standards: ASTM B408 (plate, sheet, strip), B407 (seamless pipe and tube), B409 (welded tube), B564 (forgings), ASME SB-408, SB-407, SB-409.

Typical applications include:

● Heat treatment equipment: furnace components, retorts, muffles, radiant tubes, and conveyor belts.

● Petrochemical processing: reformer tubes, cracking tubes, and heat exchangers.

● Power generation: superheater and reheater tubing in fossil-fuel power plants.

● Nuclear reactors: steam generator tubing and other high-temperature components.

● Food processing: equipment requiring resistance to hot chloride solutions.

Incoloy 800 has two common variants: Incoloy 800H (controlled carbon content 0.05–0.10 percent and grain size for improved creep-rupture strength at high temperatures) and Incoloy 800HT (aluminum and titanium controlled, plus carbon 0.06–0.10 percent for even better creep properties). For most high-temperature structural applications, 800H or 800HT are preferred over the standard 800 grade.

Comparison with other alloys: Incoloy 800 offers higher strength than stainless steel 310 at elevated temperatures, but lower strength than Inconel 600 or 601. It is less expensive than Inconel alloys due to lower nickel content. For maximum oxidation resistance above 1,100°C, Inconel 601 is better. For aqueous corrosion resistance, Inconel 625 or Alloy 20 are more suitable.

Selection guidance: Choose Incoloy 800 (or 800H/800HT) for high-temperature furnace components, petrochemical heaters, and power plant tubing requiring good creep strength and oxidation resistance up to 1,100°C, at a lower cost than high-nickel alloys. For severe carburizing or sulfidizing environments, higher-chromium alloys may be needed.