Furnace operators managing continuous high-temperature atmospheres above 600°C have a limited selection of metals capable of withstanding years of cyclic heating without scaling or structural cracking. Incoloy 800 sheet sits near the top of that list, built on a nickel-iron-chromium base that resists oxidation and carburization at once. This article breaks down what the alloy is made of, where it earns its keep, and how it stacks up against its H and HT variants.
What is Incoloy 800 Sheet?
Incoloy 800 sheet is a solid-solution, austenitic nickel-iron-chromium alloy holding roughly 30 to 35 % nickel and 19 to 23 % chromium, with iron making up the balance. The chromium forms a protective oxide layer at a certain temperature, while the nickel keeps the austenitic structure stable instead of transforming into brittle phases under heat. Fabricators buy it as flat sheet and sheet-in-coil because both forms take shearing, bending, and welding without the cracking that plagues harder alloys.
Petrochemical plants, power generation utilities, and heat-treating shops all specify Incoloy 800 Sheets for components sitting inside furnaces, reformers, and superheaters for years at a stretch. Carbon steel scales within months in that environment. Standard 300-series stainless steel oxidizes faster than plant schedules allow. Incoloy 800 sheet closes that gap, holding its strength and surface integrity through thousands of heating and cooling cycles.
Properties of Incoloy 800 Sheets
Four characteristics decide whether Incoloy 800 sheet fits a project, spanning thermal performance, surface stability, corrosion behavior, and shop-floor workability.
High-Temperature Strength
- Incoloy 800 sheet keeps useful tensile and yield strength across the full service range up to 600°C, resisting creep under sustained furnace loads.
- The alloy’s nickel-rich austenitic matrix resists softening during thermal cycling, so components hold dimensional accuracy through years of repeated heating and cooling.
Oxidation and Carburization Resistance
- The formation of a dense layer of chromium oxide on the surface at elevated temperature prevents further ingress of oxygen and slows the loss of metal during a long exposure in the furnace.
- The silicon in the alloy chemistry improves resistance to carburizing atmospheres, limiting carbon uptake in cracking furnace and pyrolysis tube service.
Corrosion Resistance
- Incoloy 800 sheet resists aqueous corrosion in mildly acidic and caustic process streams, making it suitable for nuclear steam generator tubing and piping.
- The alloy withstands sulfur-bearing atmospheres better than austenitic stainless steel grades, reducing sulfidation attack in petrochemical furnace and reformer environments.
Good Fabricability
- Sheet stock forms, shears, and cold-bends using standard stainless steel tooling, with work-hardening rates only moderately higher than 304 or 316 stainless.
- The alloy welds cleanly with matching filler wire, and post-weld heat treatment restores full mechanical properties for pressure-retaining fabrication work.
Applications of Incoloy 800 Sheets
Fabricators across five sectors specify Incoloy 800 sheet, where sustained heat, corrosive gases, and repeated thermal cycling would degrade cheaper alloys within a few years.
Petrochemical and Chemical Processing
Refineries and chemical plants use the sheet for reformer tube supports, transfer-line exchanger components, and ethylene cracking equipment exposed to cyclic thermal shock and carburizing gas streams daily.
Power Generation
Power stations fabricate superheater and reheater components from Incoloy 800 sheet, since the alloy holds strength and resists steam-side oxidation across boiler operating temperatures for decades of continuous service.
Industrial Furnaces
Industrial furnace builders use the sheet for muffles, radiant tubes, and combustion chamber linings, where oxidation resistance at sustained temperature determines how long a furnace runs before rebuild.
Heat-Treating Equipment
Heat-treating shops fabricate baskets, trays, and fixtures from Incoloy 800 sheet, since repeated quench cycling would crack lower-grade stainless within months of continuous furnace loading and unloading.
Nuclear Engineering
Nuclear plants specify the alloy for steam generator tubing and internals, where corrosion resistance in high-purity water and resistance to stress corrosion cracking matter more than raw strength.
Incoloy 800 vs Incoloy 800H vs Incoloy 800HT
Choosing between the three grades comes down to service temperature and creep life, not corrosion resistance, since all three share a near-identical base chemistry. For nickel-heavy alternatives at a higher cost, Inconel Sheets cover service conditions beyond what the 800 series handles.
- Incoloy 800 caps carbon at 0.10 percent with no fixed minimum, giving it higher room-temperature yield and tensile strength but comparatively weaker long-term creep resistance above 600°C.
- Incoloy 800H restricts carbon to a tighter 0.05 to 0.10 percent band and anneals at a coarser grain size, raising rupture strength for reformer tubes and superheater service running past 593°C.
- Incoloy 800HT pushes carbon control further still, to 0.06 to 0.10 percent, while lifting aluminum plus titanium content to 0.85 to 1.20 percent, which produces the highest creep and rupture strength of the three grades at temperatures approaching 1000°C.
| Feature |
Incoloy 800 |
Incoloy 800H |
Incoloy 800HT |
| Carbon Content |
0.10% max, no minimum |
0.05% to 0.10% |
0.06% to 0.10% |
| Strength |
Higher room-temperature yield and tensile strength |
Improved creep and rupture strength above 593°C |
Highest creep and rupture strength of the three grades |
| Temperature Range |
Up to 593°C (1100°F) |
593°C to 900°C |
Up to 1000°C, best for sustained high-temperature service |
| Typical Use |
General corrosion service, moderate-temperature components |
Reformer tubes, superheaters, pressure vessels |
Furnace radiant tubes, heat-treating baskets, high-temp fixtures |
Summary
Incoloy 800 sheet earns its place in furnaces, reformers, and steam systems because it resists oxidation, carburization, and creep at once, across decades of thermal cycling that would retire ordinary stainless steel within a few seasons. The 800H and 800HT variants extend that same base chemistry further into high-temperature, long-duration service through tighter carbon and grain-size control. Choosing the right grade depends on operating temperature, expected service life, and whether corrosion or creep drives the failure mode on site. Goodluck Metal Corporation stocks and imports Incoloy 800, 800H, and 800HT sheet and coil from established mills across multiple countries. Contact the team for a quote on sheet thickness, quantity, and mill certification for your project.
Frequently Asked Engineering Questions
What is the maximum operating temperature of Incoloy 800 sheets?
Standard Incoloy 800 sheet suits continuous service up to 593°C, while 800HT extends usable creep resistance toward 1000°C in radiant tube applications.
Is Incoloy 800 better than SS 310?
Incoloy 800 resists carburization and sulfidation better than SS 310 in furnace atmospheres, though SS 310 costs less for moderate oxidation-only service.
Can Incoloy 800 be welded easily?
Yes. The alloy welds with matching filler metal using standard TIG or MIG procedures, and post-weld heat treatment restores full mechanical properties.
Does Incoloy 800 resist chloride stress corrosion cracking?
Its high nickel content gives Incoloy 800 strong resistance to chloride stress corrosion cracking, unlike austenitic stainless steels under similar chloride exposure.