Incoloy 825
Incoloy 825 (UNS N08825) is a nickel-iron-chromium alloy with additions of molybdenum (2.5–3.5%), copper (1.5–3.0%), and titanium that provide exceptional resistance to corrosion in both oxidizing and reducing environments. It was specifically designed to resist sulfuric and phosphoric acid attack — two of the most aggressive industrial corrosives — while also providing excellent resistance to chloride stress corrosion cracking, pitting, and crevice corrosion in seawater and other chloride environments. The nickel content (38–46%) provides immunity to chloride-induced stress corrosion cracking that would affect austenitic stainless grades.
Incoloy 825 is widely used in oil and gas production, chemical processing, and aerospace applications involving aggressive fluid media. The titanium addition stabilizes the alloy against sensitization in the carbide precipitation range, preserving corrosion resistance in welded fabrications without post-weld solution annealing.
Product Forms & Size Range of Incoloy 825
Incoloy 825 bar per AMS 5873 and ASTM B425 is available in diameters from 0.250 inch to 8.000 inches, annealed. Bar is used for machined valve components, pump shafts, and structural fittings in corrosive fluid service. The AMS 5873 form is specified for aerospace applications requiring the tighter composition and property requirements of the AMS standard versus the ASTM commercial grade.
Incoloy 825 seamless pipe and tube per ASTM B423 are available in outside diameters from 0.375 inch to 10.750 inches for heat exchanger tube bundles, process piping, and aerospace fluid system tubing in aggressive environments. Tubing is produced in the annealed and pickled condition per ASTM B423 requirements.
Incoloy 825 plate, sheet, and strip per ASTM B424 are available in thicknesses from 0.010 inch to 2.000 inches for fabricated chemical vessels, aerospace fluid system panels, and heat exchanger shell components. All flat product is solution annealed and descaled for maximum corrosion resistance.
HEAT TREATMENT OF INCOLOY 825
Incoloy 825 is solution annealed at 1700–1800°F (927–982°C) followed by rapid cooling. It is not precipitation hardenable. The titanium stabilization (0.6–1.2% Ti) effectively eliminates carbide sensitization in the weld heat-affected zone, making Incoloy 825 suitable for corrosive service in the as-welded condition without post-weld heat treatment in most applications. Stress relief at 1600°F (871°C) is optional for highly restrained weldments in particularly aggressive corrosive service.
Incoloy 800
Fe-Ni-Cr alloy for high-temperature oxidizing service to 1500°F — outstanding oxidation and carburization resistance for furnace and process equipment.
Incoloy Alloy 20
Fe-Ni-Cr-Mo-Cu alloy with maximum resistance to sulfuric acid across its full concentration range — the benchmark acid-resistant nickel alloy.
Certified Material for Critical Service
Incoloy 825 is supplied to AMS 5873 (bars and forgings, aerospace grade), ASTM B423 (seamless pipe and tube), ASTM B424 (plate, sheet, strip), and ASTM B425 (bar and rod). All forms are supplied solution annealed. Corrosion testing per ASTM G28 Method A (huey test) is available on request to verify corrosion resistance in sulfuric acid environments.