Physical properties
| Density | 7.944 | g/cm³ |
Informative values: they vary with composition, condition and test method. Use the governing standard or measured mill data for pressure and heat-transfer calculations.
Chemical composition
Nominal: mid-range where both limits are given, the cap where only a maximum is, balance takes the remainder. Exact specified ranges below.
| Element | Name | Content % | |
|---|---|---|---|
| Main elements6 elements | |||
| Fe | Iron | ≥ 39.5% | |
| Ni | Nickel | 30 – 35% | |
| Cr | Chromium | 19 – 23% | |
| Al | Aluminium | 0.15 – 0.6% | |
| Ti | Titanium | 0.15 – 0.6% | |
| C | Carbon | 0.05 – 0.1% | |
| Element | Name | Content % | |
|---|---|---|---|
| Minor & residual5 elements | |||
| Mn | Manganese | ≤ 1.5% | |
| Cu | Copper | ≤ 0.75% | |
| Si | Silicon | ≤ 1% | |
| P | Phosphorus | ≤ 0.045% | |
| S | Sulphur | ≤ 0.015% | |
Mechanical minima by form
Guaranteed values differ by form, size and delivery condition; quotations confirm the specification, form, size and condition.
| Form | Condition | Rm MPa | Rp0.2 MPa | A ≥ % | Other requirements and notes |
|---|---|---|---|---|---|
| Bar and forgings | |||||
| Bar and rod | Annealed to a controlled grain size | ≥ 450 (65 ksi) | ≥ 170 (25 ksi) | ≥ 30 | |
| Bars and shapes (boiler and pressure-vessel use) | Annealed | ≥ 450 (65 ksi) | ≥ 170 (25 ksi) | ≥ 30 | Also specified: Hardness ≤ 192 HBW Hardness ≤192 HBW. |
| Plate, sheet and strip | |||||
| Plate, sheet and strip | Annealed to a controlled grain size | ≥ 450 (65 ksi) | ≥ 170 (25 ksi) | ≥ 30 | |
| Tube and pipe | |||||
| Seamless pipe and tube | Hot-finished annealed or cold-worked annealed | ≥ 450 (65 ksi) | ≥ 170 (25 ksi) | ≥ 30 | |
| Welded pipe and tube | Annealed, N08810 | ≥ 450 (65 ksi) | ≥ 170 (25 ksi) | ≥ 30 | |
| Welded pipe and tube | Annealed, N08810 or N08811 | ≥ 450 (65 ksi) | ≥ 170 (25 ksi) | ≥ 30 | |
| Seamless pressure tubes (EN 10216-5, wall ≤50 mm, 1.4958 / 1.4959) | +AT (solution annealed) | 500 – 750 | ≥ 170 | ≥ 35 | Rp1.0 ≥ 200 MPa; transverse A ≥ 30 %; KV ≥ 120/80 J (long./transv.); 1.4958+RA: Rp0.2 ≥ 210 MPa. |
| Fittings and flanges | |||||
| Fittings (factory-made wrought butt-weld / socket) | 2100-2150 °F [1147-1177 °C], rapid air or water quench | — | — | — | Recommended temperature; tolerance ±15 °C (±25 °F). Tensile properties follow the starting material. No tension test on the finished fitting unless agreed. Heat treatment depends on the service temperature; agreed with the producer. |
| Fittings (wrought austenitic stainless, butt-weld / socket) | Solution annealed 2100–2150 °F [1149–1177 °C], water quenched or otherwise rapidly cooled | ≥ 450 (65 ksi) | ≥ 170 (25 ksi) | ≥ 28 | Elongation: ≥28% longitudinal, ≥20% transverse. A single temperature is a minimum. All fittings are supplied heat-treated. Heat treatment depends on the service temperature; agreed with the producer. |
| Several forms | |||||
| Long products d ≤160 mm and flat products (EN 10302, 1.4958 / 1.4959) | +AT (solution annealed) | 500 – 750 | ≥ 170 | ≥ 35 | Flat products: A ≥ 30 %. 1.4958 recrystallisation annealed (+RA): Rp0.2 ≥ 210 MPa. |
Creep behaviour
Guidance values (MPa) — Mean values of a scatter band. They are neither an acceptance requirement nor a design allowable stress. Figures in parentheses are long-term extrapolations and less reliable than the tested range.
| Temp °C | Creep strength Rp1.0 (1% plastic strain) | Rupture strength Ru | ||
|---|---|---|---|---|
| 10 000 h | 1 000 h | 10 000 h | 100 000 h | |
| 600 | 90 | 200 | 152 | 114 |
| 700 | 40 | 90 | 68 | 48 |
| 800 | 15 | 45 | 30 | 21 |
| 900 | 5 | 20 | 10 | 8 |
The table above is for the +AT (solution-annealed) condition (W.Nr. 1.4876 X10NiCrAlTi32-21).
Rp1.0 is the stress producing 1 % plastic elongation and Ru the stress to rupture; at the same temperature and time Rp1.0 is necessarily below Ru. Design deflection-sensitive parts to Rp1.0 and design to fracture with Ru.
1 000 h strength for 1 % elongation: 130 MPa at 600 °C, 70 at 700 °C, 30 at 800 °C and 13 at 900 °C.
⚠ The table above is for EN 1.4876 X10NiCrAlTi32-21, which has neither a carbon minimum nor a coarse-grain requirement. N08810 (800H) carries two requirements beyond it: a carbon floor of 0.05-0.10 % and solution annealing at 1093 °C or above to an ASTM grain size of 5 or coarser. Both exist specifically to raise creep life.
⚠ The table above is therefore a CONSERVATIVE reference for N08810: conforming 800H should perform at least this well, but the table cannot be used to pass or fail 800H and does not replace its own stress-rupture testing. A creep guarantee for 800H has to rest on a grain-size requirement written into the order and on the manufacturer's long-term data.
⚠ The maximum application temperature in air, Tₐ = 1 100 °C, is an oxidation criterion, not a load-bearing one.
Grain size
Required by the standard — ASTM No. 5 or coarser
Mean grain diameter approx. ≥ 63.5 μm
Mandatory acceptance requirement in the annealed condition.
More detail 1
The coarse grain is the source of 800H/800HT creep and stress-rupture performance — too fine a grain is a rejection, the opposite of the usual "finer is better" instinct.
Where this grade is recommended
Matched in 12 service conditions; ranks and scores computed from the condition-scoring matrix.
| Service condition | Industry | Temperature | Rank | Score |
|---|---|---|---|---|
| Hydroprocessing & refinery hot service | Oil & Gas | 250 – 400 °C | 2 / 8 | 90 |
| DeNOx SCR & ducting | Environmental & FGD | 320 – 400 °C | 1 / 5 | 88 |
| Quench & carburising fixtures | Furnaces & Vacuum | 850 – 950 °C | 4 / 8 | 88 |
| Muffles & radiant tubes | Furnaces & Vacuum | 850 – 1000 °C | 6 / 9 | 88 |
| HT boiler & superheater | Power & Nuclear | 450 – 600 °C | 5 / 6 | 87 |
| CSP & molten-salt receivers | Hydrogen & New Energy | 300 – 565 °C | 4 / 4 | 86 |
| Exhaust systems & converters | Automotive & Racing | 400 – 700 °C | 3 / 5 | 85 |
| Furnace internals & fixtures | Furnaces & Vacuum | ≤ 900 °C | 11 / 12 | 85 |
| Nuclear SG tubing | Power & Nuclear | 300 – 350 °C | 3 / 4 | 84 |
| SOFC interconnects | Hydrogen & New Energy | 600 – 850 °C | 3 / 4 | 84 |
| Waste-to-energy boilers | Environmental & FGD | 450 – 700 °C | 8 / 8 | 82 |
| Nuclear fuel cladding & grids | Power & Nuclear | ≤ 350 °C | 4 / 4 | 78 |
Designations & equivalents
| UNS | N08810 / N08811 |
| W.Nr. (Germany) | 1.4958 / 1.4959 |
| EN designation | X5NiCrAlTi31-20 / X8NiCrAlTi32-21 |
| Trade name(s) | Incoloy 800H / 800HT |
| ASTM / AISI | A182 / A240 / A276 / A403 / A479 / A484 / B163 / B366 / B407 / B408 / B409 / B514 / B515 / B564 |
| JIS (Japan) | NCF800H |
| GOST (Russia) | ≈ ХН32Т (ЭП670) |
800H (N08810) and 800HT (N08811) have the same room-temperature strength but different composition — state the UNS number on the order. 800HT requires 0.06–0.10 % carbon and 0.25–0.60 % each of aluminium and titanium, 0.85–1.20 % combined; 800H requires 0.05–0.10 % carbon.
Cross-references are common near-equivalents for search and shortlisting; substitution across standards requires clause-by-clause verification. All grades in one cross-reference table →
Applicable standards
13 specifications. Name the standard and its edition on the order.
From its 2026 edition ASTM B163 no longer covers N08800, N08810 or N08811.
More detail 1
For new heat-exchanger tube orders use B407, or state B163-22 in the contract.
Guaranteed values and required tests differ between specifications — see Mechanical minima by form for the figures per form.
Frequently asked questions
What is Alloy 800H / 800HT · UNS N08810?
Alloy 800H / 800HT · UNS N08810 — Fe-Ni superalloys. Carbon-controlled creep grade — 900 °C-class pressure parts
What is the maximum service temperature of N08810?
Typically about 900 °C; the practical limit depends on media, stress and design life — acceptance per the governing standard.
What is the tensile strength of N08810?
The specified minimum tensile strength is 450 MPa for the main product form. Minima for other forms and sizes are listed under "Mechanical minima by form" on this page.
Which standards cover N08810?
ASTM A182, ASTM A240/A240M, ASTM A276, ASTM A403, ASTM A479/A479M, ASTM B407, ASTM B408, ASTM B409, ASTM B514, ASTM B515, ASTM B564 (forgings), EN 10302 (creep-resisting steels, nickel and cobalt alloys), EN 10216-5 (seamless pressure tubes)
Where is N08810 typically used?
Hydroprocessing & refinery hot service (Oil & Gas); DeNOx SCR & ducting (Environmental & FGD); Quench & carburising fixtures (Furnaces & Vacuum); Muffles & radiant tubes (Furnaces & Vacuum)
In which forms is N08810 available?
Tube, plate, strip, bar, forgings, wire and other forms — sizes and delivery condition confirmed per order, with EN 10204 3.1 / 3.2 certification.
Same series
Download PDF datasheet
This grade’s datasheet as an A4 PDF — for filing, printing or forwarding to colleagues.
Download PDF datasheetSupply & enquiry
Tube & pipeφ1 – 219 × 0.25 – 25 mm
Plate4.76 – 80 mm
Barφ8 – 300 mm
Wire & filler metalsφ0.01 – 8 mmFor this grade we can supply, against your service conditions:
- Tube, plate, strip, bar, forgings, wire and more — with size range and lead time
- Chemistry and mechanical test report (EN 10204 3.1 / 3.2)
- Like-for-like alternatives and selection advice
- Applicable standards and inspection scope
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