NeoNickel supplies Alloy 800H/AT, a high-strength nickel alloy 800 grade for high temperature structural applications. Available in sheet, plate, round bar, pipe and tube.
Alloy 800H/AT (also known as Incoloy 800H/HT) is an austenitic heat-resistant nickel alloy 800 grade designed for high temperature structural applications. Its strength is achieved through controlled levels of carbon, aluminium and titanium, combined with a 1148°C minimum anneal that produces a grain size of ASTM 5 or coarser.
This combination gives Alloy 800H/AT significantly higher creep and stress-rupture strength than standard Alloy 800, along with strong resistance to oxidation, carburisation and nitrogen absorption from nitriding atmospheres. These properties make it a dependable alloy 800 material across petrochemical, power generation and thermal processing industries.
Key Benefits of Alloy 800H/AT:
We stock Alloy 800H/AT in a range of product forms to suit different applications and fabrication methods, including sheet, plate, round bar, pipe (seamless), pipe fittings and flanges. To view available sizes and submit an enquiry, use the dropdown selector below.
The following elements in Alloy 800H/AT provide its distinctive balance of high-temperature strength and resistance to oxidation, carburisation and creep.
| % | Cr | Ni | Si | C | Mn | P | S | Cu | Fe | Al | Al+Ti |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Min | 19 | 30 | 0.06 | 39.5 | 0.15 | 0.85 | |||||
| Max | 23 | 35 | 1 | 0.1 | 1.5 | 0.045 | 0.015 | 0.75 | 0.6 | 1.2 |
Alloy 800H/AT is built for long service at high temperatures in oxidising, carburising and nitriding atmospheres. Key physical and thermal properties include:
Alloy 800H/AT is part of the nickel alloy 800 family, developed for high-temperature strength, creep resistance and stability in oxidising, carburising and nitriding atmospheres. It is dual-certified to both UNS N08810 (800H) and UNS N08811 (800HT), combining the chemistry and mechanical property requirements of both grades.
The difference between standard Alloy 800 and the H/AT variants comes down to three controlled parameters:
Together, these modifications produce a material with significantly higher creep-stress rupture strength than standard Alloy 800, making 800H/AT the preferred alloy 800 material for structural service above 540°C.
Alloy 800H/AT can be welded using standard nickel alloy techniques, with filler metal selection based on service temperature and strength requirements:
To avoid stress-relaxation grain-boundary cracking in service above 538°C, welded fabrications can be heat treated at 899°C for around one hour per inch of thickness (30 minutes minimum), followed by air cooling.
NeoNickel supplies Alloy 800H/AT in sheet, plate, round bar, pipe and tube, all with full mill certification and traceability, supported by technical guidance from our specialist team.
| Mechanical & Physical Properties | 21.1°C | 537.8°C | 649°C | 760°C | 871°C | 982°C |
|---|---|---|---|---|---|---|
| Ultimate Tensile Strength /MPa | 530.9 | 437.8 | 384 | 222.7 | 128.2 | 70.3 |
| 199.9 | 113.8 | 102 | 99.3 | 80 | 61.4 | |
| - | - | - | - | - | - | |
| 52 | 51 | 50 | 78 | 120 | 120 | |
| - | - | - | 41.4 | 24.8 | 7.2 | |
| - | - | - | 50.3 | 24.1 | 8.3 | |
| - | - | - | 17.8 | 18.4 | - | |
| 10 | - | - | 20.5 | 22.5 | 26.5 | |
| 1.97 | - | - | 1.45 | 1.32 | - |
With its high-temperature strength, creep resistance and resistance to oxidation and carburisation, Alloy 800H/AT is used across industries where materials must perform reliably under prolonged heat and corrosive attack. Alloy 800 plate is commonly fabricated into pressure vessels and structural sections, while alloy 800 pipe and alloy 800 tube are widely specified for fluid-handling systems exposed to sustained heat.
Its ability to maintain strength and resist oxidation, carburisation and creep at elevated temperatures makes Alloy 800H/AT a reliable choice for components operating in demanding, high-heat environments.
A dual-certified iron-nickel-chromium alloy (UNS N08810 / N08811) designed for high-temperature structural applications. Controlled carbon, aluminium and titanium levels combined with a coarse grain size give it higher creep and stress-rupture strength than standard Alloy 800.
All three share the same Fe-Ni-Cr composition. Alloy 800 (N08800) has a 0.10% carbon maximum and no grain size requirement. Alloy 800H (N08810) has 0.05 to 0.10% carbon with ASTM grain size 5 or coarser. Alloy 800HT (N08811) adds a restricted Al+Ti range of 0.85 to 1.20% for the highest creep strength of the three.
30 to 35% nickel, 19 to 23% chromium and 39.5% iron minimum, with controlled additions of carbon, aluminium and titanium.
It is used for structural service up to around 1100°C, with its creep strength advantage over standard Alloy 800 most pronounced above 540°C.
Yes. It resists oxidation, carburisation and nitrogen absorption from nitriding atmospheres, and the high nickel content gives strong resistance to chloride stress-corrosion cracking.
Yes, using standard processes including GTAW, GMAW and SMAW. Recommended filler metals include ERNiCr-3, UNS N08334 or ERNiCrCoMo-1 depending on service temperature.
It belongs to the Incoloy 800 family but is a distinct grade. Incoloy® is a registered trademark of Special Metals Corporation, and Alloy 800H/AT corresponds to Incoloy 800H/800HT.
Sheet, plate, round bar, pipe (seamless), pipe fittings and flanges.
NeoNickel supplies Alloy 800H/AT across the UK and Europe, supporting both urgent requirements and long-term project needs. All material is provided with full mill certification and traceability, meeting relevant international standards. Our team can assist with material selection, specifications and product forms.
If you're unsure which grade or form is right for your application, fill out our enquiry form and a member of the team will be in touch.
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