Specifications

Chemical composition and mechanical properties

Alloy 800HT also requires Al + Ti 0.85–1.20%. Alloys 800H and 800HT have grain size and heat-treatment requirements for elevated-temperature service, as given in the standards.

Values common to ASTM B407, B409 and B408 (alloy 800 family), B423, B424 and B425 (alloy 825) and B564 forgings; check the standard for the product form and size.

Background and equivalents are on the Incoloy page.

Incoloy 800H plate for high-temperature equipment

Incoloy 800H and 800HT plates and sheets are used for components that operate above about 600 °C for long periods: reformer and cracking furnace parts, transfer-line and outlet-header components, furnace muffles, retorts and radiant tubes, heat-treatment baskets and fixtures, and petrochemical heaters. Their creep strength, resistance to oxidation, carburisation and nitriding, and stable structure make them a standard choice where stainless steels such as 310S would lose strength or become brittle. Alloy 800 in the annealed condition is used for heat-exchanger and process equipment at lower temperatures.

Incoloy 825 plate for acid and chloride service

Incoloy 825 plates and sheets are used for vessels, tanks, heat exchangers and linings handling sulphuric acid, phosphoric acid, pickling solutions and chloride-bearing process streams, and for flue-gas desulphurisation and scrubber equipment. Titanium stabilisation keeps welded joints resistant to intergranular corrosion. Compared with 316L, alloy 825 offers much better resistance to chloride stress corrosion cracking and reducing acids, at a lower cost than the most highly alloyed nickel-chromium-molybdenum alloys. Carbon steel plate clad with 825 is also used for large vessels and for clad line pipe.

Fabrication

Incoloy plates form readily cold and hot. Hot forming is done in a sulphur-free atmosphere. For 800H and 800HT in creep service, heavy cold forming may need a re-solution anneal to restore the coarse-grained structure, as the design code specifies. Welding uses nickel-based filler metals – ERNiCr-3 or matching 800H fillers for the alloy 800 family, and ERNiCrMo-3 for 825 – on clean joints. Plate is cut by plasma or water-jet, not by oxy-fuel.

Grain size and testing

For 800H and 800HT, ASTM B409 sets carbon, aluminium and titanium limits and requires a minimum average grain size, which the mill reports on the certificate. Plates for pressure parts are often ordered with ultrasonic testing. For 825 in acid service, an intergranular corrosion test can be added. Please list any supplementary requirement with the enquiry.

Ordering Incoloy sheets and plates

Please give the alloy and specification, thickness, width and length or cut size, condition, quantity and any testing or inspection. Sheets are packed flat on pallets with interleaving, and plates on wooden skids; each piece is marked with alloy, specification, heat number and size and is traceable to its mill test certificate.

Applications and related products

Incoloy sheets and plates are used for furnace and heat-treatment equipment, reformer and cracker components, heat exchangers, acid plant vessels and linings, scrubbers and clad equipment. Matching products include Incoloy pipes and tubes, Incoloy round bars, Incoloy flanges, Incoloy pipe fittings and Incoloy fasteners. Other materials are on our plates and sheets pages.