Specifications

Composition and properties

Nickel includes cobalt where stated in the standard. Footnotes as given in each ASTM specification.

Values for Grade 1 annealed material; size limits and Grade 2 (solution annealed) properties as given in each standard.

Inconel 600 plate is lower in strength than 625; its annealed properties and those of 601 and 718 are as given in ASTM B168 and B670 and are reported on the mill test certificate.

Choosing between 600, 601 and 625 plate

For high-temperature equipment exposed to oxidising atmospheres – heat-treatment baskets, retorts, muffles and furnace hardware – alloy 600 is the classic choice, and alloy 601 is chosen where temperatures are higher still or thermal cycling causes scale to spall, because its aluminium content forms a more adherent oxide. For wet corrosion – seawater, chloride-contaminated acids, flue gas condensate – and for strength, alloy 625 is preferred; its higher strength also allows thinner sections. Alloy 718 plate is used where an age-hardened, very high-strength part is machined from plate. The alloy, specification and condition should be stated together on the order.

Inconel plate in cladding and lining

Because nickel alloys are expensive, many vessels and pipes use a carbon steel shell for strength with a corrosion-resistant layer of alloy 625 on the wetted side – by roll bonding, explosion bonding, weld overlay or loose lining with Inconel sheet. Thin Inconel sheet is also used to line ducts, stacks and scrubbers in flue gas desulphurisation units. For these applications, sheet thickness, flatness and surface condition matter for welding to the backing steel; please describe the intended use so suitable material can be offered.

Fabrication notes

Inconel sheet and plate form well cold but work-harden quickly, so heavy forming may need intermediate annealing. Welding uses matching or over-alloyed nickel filler metals, clean joints free of sulphur, lead and phosphorus, and low heat input. Thermal cutting is usually by plasma or laser, with the cut edges dressed before welding. Material should be stored away from carbon steel and contamination.

Ordering

Please give the alloy and UNS number, ASTM specification, condition, thickness, width, length, quantity and any supplementary tests or inspection required.

Heat resistance and oxidation

In heat-treatment furnaces and kilns, Inconel plate and sheet must resist scaling, carburisation and nitriding as well as keep their shape under load at high temperature. Alloy 600 forms a protective chromium oxide; alloy 601 adds aluminium to form a tighter oxide that stays attached during thermal cycling, which is why it is favoured for muffles, radiant tubes and baskets that are heated and cooled repeatedly. Design for these parts also allows for thermal expansion and creep, so section thickness and support spacing are part of the engineering, not only the alloy choice.

Applications and related products

Inconel sheets and plates are used for furnace and heat-treatment equipment, chemical reactors and vessels, flue gas desulphurisation scrubbers and ducts, nitric acid and caustic plants, seawater and offshore equipment, aerospace and turbine parts, and cladding and lining of carbon steel equipment. To complete an Inconel project we also supply Inconel pipes and tubes, Inconel round bars, Inconel wires, Inconel flanges, Inconel pipe fittings and Inconel fasteners. Other plate and sheet materials are on the plates and sheets pages, and alloy guidance on the Inconel page.