Nickel Alloy Incoloy 800HT
UNS N08811 · EN 1.4959
Incoloy 800HT (N08811, 1.4959) is an Fe-Ni-Cr austenitic heat-resistant alloy that differs from Alloy 800H by a controlled higher Al+Ti content, optimized for maximum creep-rupture strength and long-term microstructural stability above 1000 °C.
Reference datasheet — Incoloy 800HT is not in the instant-quote catalog. Upload your part and an engineer will quote it in this grade or suggest the closest stocked equivalent.
Values for the ANN condition
Incoloy 800HT tempers and conditions
Incoloy 800HT is supplied in 7 conditions, soft to hard. ANN is the default FabDigit quotes; the values on this page are for it.
Compare all 7 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed 1150 °C | Choose for long-term service above 900 °C (cracking coils, reformer and radiant tubes) where creep-rupture life dominates over room-temperature strength. | 215 | 500 | 48 | 130 HB | 1.8 % IACS |
ANNDefault Annealed | Standard stocked condition for pressure vessels, furnace parts and formed components; best combination of ductility and creep strength. | 240 | 520 | 45 | 140 HB | — |
Hot-worked and annealed bar | Use for bar that must be code-qualified for elevated-temperature/creep service or heavily machined without distortion. | 240 | 520 | 45 | 145 HB | 1.8 % IACS |
Cold-worked and annealed | Standard condition for seamless heat-exchanger and furnace tubing: annealed properties with cold-finished dimensional accuracy and bright surface. | 250 | 540 | 43 | 150 HB | 1.8 % IACS |
Hot-worked | Economical bar/forging condition for machined furnace fixtures where slightly higher yield and lower ductility are acceptable. | 280 | 560 | 38 | 160 HB | 1.8 % IACS |
As-welded deposit | Reference condition for fabricated assemblies; joint strength approaches annealed base metal but creep strength of the weld is lower than 800HT base. | 300 | 550 | 33 | 165 HB | 1.7 % IACS |
Cold drawn | Pick for close-tolerance fasteners, pins and instrument tubing needing higher room-temperature strength; not for creep service without re-anneal. | 500 | 680 | 25 | 210 HB | — |
What is Incoloy 800HT?
Incoloy 800HT (N08811, 1.4959) is an Fe-Ni-Cr austenitic heat-resistant alloy that differs from Alloy 800H by a controlled higher Al+Ti content, optimized for maximum creep-rupture strength and long-term microstructural stability above 1000 °C. In the annealed condition it runs about 240 MPa yield, 520 MPa tensile, 45% elongation and 140 HB (75 HRB), with service temperatures to 1100 °C; standard forms are seamless and welded tube, plate, sheet, bar and forgings. It is not precipitation hardenable and gives no room-temperature strength advantage, so it is specified only where long-term creep, oxidation and carburisation resistance justify the cost. Alloy 800H is the nearest alternative when the coarse-grain, high-Al+Ti creep requirement is less severe. Incoloy 800HT has a density of 7.94 g/cm³ (0.287 lb/in³), lighter than 88% of nickel alloy grades. It melts at 1,357°C (2,475 °F). Incoloy 800HT has a yield strength of 240 MPa (34.8 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 90% of nickel alloy grades. Elongation at break is 45% and the elastic modulus is 196 GPa (28.4 Msi).
What is Incoloy 800HT used for?
- ethylene furnace tubes
- hydrogen reformer components
- catalyst support baskets
Advantages
- Low embodied carbon — 7.5 kg CO₂/kg, better than 96% of nickel alloy grades
- High service temperature — 1,100°C (2,012 °F), better than 88% of nickel alloy grades
- High electrical conductivity — 1.8 % IACS, better than 81% of nickel alloy grades
Limitations
- Low strength — 240 MPa (34.8 ksi), worse than 90% of nickel alloy grades
Incoloy 800HT properties
Typical room-temperature values for Incoloy 800HT-ANN; bars are the position among nickel alloy grades.
Physical3
Incoloy 800HT has a density of 7.94 g/cm³ (0.287 lb/in³), lighter than 88% of nickel alloy grades. It melts at 1,357°C (2,475 °F).
Mechanical13
Incoloy 800HT has a yield strength of 240 MPa (34.8 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 90% of nickel alloy grades. Elongation at break is 45% and the elastic modulus is 196 GPa (28.4 Msi).
Thermal6
Incoloy 800HT is rated for continuous service to 1,100°C (2,012 °F). It conducts heat at 11.5 W/m·K (6.64 BTU/hr·ft·°F), better than 57% of nickel alloy grades. Thermal expansion is 14.4 µm/m·K (8 µin/in·°F).
Electrical3
Incoloy 800HT conducts electricity at 1.8 % IACS, better than 81% of nickel alloy grades.
Chemical & Environmental3
Corrosion resistance is very good (70/100), worse than 77% of nickel alloy grades.
Sustainability4
Producing a kilogram of Incoloy 800HT takes about 110 MJ of energy and emits 7.5 kg of CO₂ — less than 93% of nickel alloy grades. Typical recycled content is 40%.
Manufacturability7
Incoloy 800HT's machinability is poor (28/100, better than 82% of nickel alloy grades); weldability very good (75/100); formability very good (70/100).
Common Calculations5
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Strength versus weight in the nickel alloy family
Yield strength against density for every nickel alloy grade FabDigit runs. Incoloy 800HT is highlighted; hover a dot for its name, or open the interactive family chart.
Working with Incoloy 800HT
Is Incoloy 800HT easy to machine?
Treat like a gummy austenitic Ni alloy: rigid setup, positive-rake carbide or ceramic, low speed with heavy feed, flood coolant and never dwell — it work-hardens instantly.
Can Incoloy 800HT be welded?
Readily welded by GTAW/GMAW/SMAW with ERNiCr-3 (Alloy 82) or ENiCrFe-3; no preheat or PWHT needed, keep heat input low and interpass clean to avoid hot cracking.
Can Incoloy 800HT be formed, bent or molded?
Formable hot (1150–900 °C) and cold, but springback and forming loads are high; intermediate anneals at ~980–1050 °C are usual, and final creep parts should be re-annealed at ≥1120 °C for coarse grain.
Incoloy 800HT chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Ni | 30 – 35 | 32.5 |
| Cr | 19 – 23 | 21 |
| Chigher C than 800H for creep strength | 0.06 – 0.1 | 0.08 |
| Al | 0.25 – 0.6 | 0.45 |
| Ti | 0.25 – 0.6 | 0.45 |
| Al+Tikey 800HT requirement | 0.85 – 1.2 | 1 |
| Mn | ≤ 1.5 | 0.8 |
| Si | ≤ 1 | 0.4 |
| Cu | ≤ 0.75 | 0.3 |
| S | ≤ 0.02 | 0 |
| Febalance, 39.5 % min per ASTM | ≥ 39.5 (balance) |
What surface finishes work on Incoloy 800HT?
Pickle/passivate or grit-blast plus pickling to remove the tenacious Cr-rich scale; can be mechanically polished, but no anodising — a service-formed adherent oxide is the working surface.
Surface treatments FabDigit runs on nickel alloy parts — pick them in the quote configurator or call them out on the drawing. Each links to its datasheet in the surface-finish library (thickness, specs, call-out, material verdicts).
Plating
Thermal Spray
Equivalent designations
Standards and trade names that resolve to Nickel Alloy Incoloy 800HT in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.
- UNS
- N08811
- EN / DIN / Werkstoff-Nr.
- 1.4959
- Other
- B407/B408/B409Incoloy800HT
How much does Incoloy 800HT cost?
Incoloy 800HT is a high-cost nickel alloy ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Incoloy 800HT — frequently asked
What is Incoloy 800HT used for?
Incoloy 800HT is typically used for ethylene furnace tubes, hydrogen reformer components and catalyst support baskets. In short: highest-creep 800-series grade; stable above 1000 °C; furnace tube standard.
What is the yield strength of Incoloy 800HT?
Incoloy 800HT has a typical yield strength of 240 MPa (34.8 ksi) and a tensile strength of 520 MPa (75.4 ksi) — weaker than 90% of nickel alloy grades. Strength varies by condition: see the 7 listed tempers.
Is Incoloy 800HT easy to machine?
Not especially — machinability is rated poor (28/100, better than 82% of nickel alloy grades). Treat like a gummy austenitic Ni alloy: rigid setup, positive-rake carbide or ceramic, low speed with heavy feed, flood coolant and never dwell — it work-hardens instantly.
Can Incoloy 800HT be welded?
Yes — weldability is rated very good (75/100). Readily welded by GTAW/GMAW/SMAW with ERNiCr-3 (Alloy 82) or ENiCrFe-3; no preheat or PWHT needed, keep heat input low and interpass clean to avoid hot cracking.
What surface finishes work on Incoloy 800HT?
Pickle/passivate or grit-blast plus pickling to remove the tenacious Cr-rich scale; can be mechanically polished, but no anodising — a service-formed adherent oxide is the working surface.
Can Incoloy 800HT be formed, bent or molded?
Formable hot (1150–900 °C) and cold, but springback and forming loads are high; intermediate anneals at ~980–1050 °C are usual, and final creep parts should be re-annealed at ≥1120 °C for coarse grain.
What is the maximum service temperature of Incoloy 800HT?
Incoloy 800HT is rated for continuous use to about 1,100°C (2,012 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Incoloy 800HT-ANN and Incoloy 800HT-CD?
ANN is the default condition — standard stocked condition for pressure vessels, furnace parts and formed components; best combination of ductility and creep strength. CD: pick for close-tolerance fasteners, pins and instrument tubing needing higher room-temperature strength; not for creep service without re-anneal. Yield strength is 240 MPa in ANN versus 500 MPa in CD.
How much does Incoloy 800HT cost?
Incoloy 800HT is a high-cost nickel alloy ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.
Sources
- ASTM B409 — Ni-Fe-Cr Alloy Plate, Sheet and Strip — ASTM International (2021)
- ASTM B408 / B407 — Ni-Fe-Cr Alloy Rod & Bar / Seamless Pipe & Tube — ASTM International (2021)
- INCOLOY alloys 800H & 800HT publication SMC-047 — Special Metals Corporation (2004)
- ASME BPVC Section II Part D — allowable stresses and physical properties for N08811 — ASME (2023)
- EN 10095 / DIN 17742 material 1.4959 (X8NiCrAlTi32-21) — CEN / DIN (2018)
- ASM Handbook Vol. 1 — Heat-Resistant and Superalloys — ASM International (1990)
Property data is compiled from published supplier and standards handbooks and normalised for comparison; hardness values on non-Brinell scales are converted approximately for charting only. Manufacturability limits are FabDigit quote-engine defaults and may be relaxed by engineering review. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.