Incoloy 803
Incoloy 803 (UNS S35045) is a high-alloy iron-nickel-chromium alloy with elevated chromium content (25–29% Cr) and balanced nickel (30–35% Ni) specifically designed for the most demanding high-temperature carburizing, oxidizing, and nitriding environments encountered in thermal processing and petrochemical furnace applications. The high chromium content provides outstanding scaling resistance at temperatures up to 2100°F (1149°C), while the balanced Fe-Ni-Cr composition delivers excellent resistance to cyclic thermal shock — a critical property for furnace components subject to repeated heating and cooling cycles.
AMS 5803 governs Incoloy 803 for aerospace and industrial high-temperature applications. The alloy excels in applications where competitive grades like Incoloy 800 and 321 SS are approaching their oxidation resistance limits.
Product Forms & Size Range of Incoloy 803
Incoloy 803 bar per AMS 5803 is available in round bar from 0.188″ to 6.000″, annealed. Used for precision machined furnace fixtures, thermocouple protection tubes, furnace support hardware, and high-temperature structural components in carburizing and nitriding furnace environments.
Incoloy 803 tube and pipe per AMS 5803 is available in outside diameters from 0.125″ to 4.000″, annealed. Used for radiant tubes in continuous-atmosphere furnaces, heat exchanger tubing in high-temperature petrochemical service, and process tubes in reforming and cracking units operating beyond the capability of standard Alloy 800H.
HEAT TREATMENT OF INCOLOY 803
Incoloy 803 is solution annealed at 2000–2050°F (1093–1121°C) with rapid water quench to achieve a uniform single-phase austenitic microstructure free of carbide precipitation. The high chromium content of 803 vs 800 requires slightly higher annealing temperatures to dissolve chromium carbides. For applications requiring maximum creep and rupture resistance, a separate stabilization anneal at 1600–1700°F is specified to precipitate fine M₂₃C₆ carbides at grain boundaries.
Incoloy 800
Standard Fe-Ni-Cr alloy for high-temperature service — used where 803-level carburization resistance is not required and lower cost is preferred.
Alloy 230
Ni-Cr-W alloy with exceptional long-term high-temperature strength — used when 803 lacks sufficient creep resistance for the highest-temperature structural applications.
Certified Material for Critical Service
Incoloy 803 is supplied to AMS 5803. Mill certifications document the high chromium content (25–29%), nickel-iron balance, and mechanical properties in the annealed condition. Material must conform to the chemical composition and property requirements of AMS 5803 for all aerospace and industrial high-temperature applications.