Incoloy 800
Incoloy 800 (UNS N08800) is an iron-nickel-chromium alloy with titanium and aluminum additions that resist high-temperature oxidation, carburization, and nitriding. It has a carbon maximum of 0.10% and no grain size requirement. As the baseline variant in the Alloy 800 family, it is suited for moderate elevated-temperature service up to approximately 760 degrees C.
1. Chemical Composition
The table below shows the elemental limits for Incoloy 800. The iron-nickel-chromium balance and combined Ti+Al constraint define its high-temperature stability characteristics.
| GRADE | UNS Designation |
Standard (Pipe) |
Chemical Requirement (Max) | |||||||||||
| C | Mn | P | S | Si | Ni | Cr | Mo | Cu | Fe | Ti | Al | |||
| Incoloy 800 | N08800 | B407 | ≤0.10 | ≤ 1.50 |
≤ 0.045 |
≤ 0.015 |
≤ 1.00 |
30.0- 35.0 |
19.0-23.0 | - | ≤0.75 | ≥ 39.5 | 0.15-0.6 | 0.15-0.6 |
2. Mechanical Properties
The table below presents room-temperature mechanical property minimums for Incoloy 800 pipe and tube in the annealed condition, per ASTM B407.
| Grade | Condition & Size | Standard | Tensile Strength , MPa (ksi) |
Yield Strength MPa (ksi) | Elongation , % |
Hardness |
| N08800 | Cold-worked annealed | B407 | ≥520（75） | ≥205（30） | ≥30 | — |
| N08800 | Hot-finished annealed or hot-finished | B407 | ≥450（65） | 170 (25) | ≥30 | — |
3. Equivalent Grade
The table below maps Incoloy 800 (UNS N08800) to its equivalent designations across EN/DIN, JIS, GB/T, ISO, and GOST standards.
| GRADE | UNS | GB | JIS | ISO | DIN/EN | GOST | |
| ISC | NEW | ||||||
| Incoloy 800 | N08800 | - | NS110 | NCF800 | - | 1.4876 | - |
3. Key Technical Advantages
- Austenitic Stability at Elevated Temperatures: The nickel-iron-chromium chemistry of Incoloy 800 maintains a fully austenitic structure at all temperatures. It does not undergo the ferritic or martensitic transformation that limits the high-temperature performance of lower-nickel iron-base alloys.
- Baseline Alloy 800 Variant for General Service: With a carbon ceiling of 0.10% and no grain size specification, Incoloy 800 is the standard-grade option for applications where thermal stability requirements do not call for the controlled carbon and grain size of the 800H or 800HT variants.
- Resistance to Carburizing and Nitriding Atmospheres: The combined titanium and aluminum content (min 0.30% combined Al+Ti) selectively getters carbon and nitrogen at the surface, reducing penetration of these species into the metal matrix in furnace and pyrolysis tube environments.
- Technical Note: Incoloy 800 is not interchangeable with 800H or 800HT in ASME pressure vessel code applications above 540 degrees C. At elevated temperatures, code allowable stresses require the controlled carbon and grain size of 800H or 800HT. Specify the correct sub-grade based on design temperature.
4. Common Manufacturing Standards
- ASTM B407: Standard Specification for Seamless Pipe and Tube, Nickel-Iron-Chromium Alloy (UNS N08800, N08810, N08811). This is the primary standard covering Incoloy 800 seamless pipe and tube for industrial heat exchanger and furnace applications.
- DIN/EN Standards:
EN 10216-5: Seamless steel tubes for pressure purposes, nickel alloy grades (Material No. 1.4876)
DIN 17459: Seamless circular tubes made of nickel alloys - JIS Standards:
JIS H 4552: Nickel and nickel alloy seamless pipes and tubes - GB/T Standards:
GB/T 15007: Corrosion-resistant alloy grades (NS1102) - GOST Standards:
GOST 14965: Tubes from nickel and nickel alloys
Summary Table — Standard Equivalents:
| ASTM | EN/DIN | JIS | GB/T | GOST |
| ASTM B407 | EN 10216-5 / DIN 17459 | JIS H 4552 | GB/T 15007 | GOST 14965 |
5. Primary Applications
- Heat Exchanger Tubes in Petrochemical Plants: Transfer of process fluids at elevated temperatures in refinery heat exchangers where both corrosion resistance and moderate high-temperature strength are needed below 760 degrees C.
- Industrial Furnace Tubes and Muffles: Atmosphere-bearing furnace components in annealing and carburizing furnaces where resistance to oxidizing and carburizing gases is needed up to intermediate temperatures.
- Nuclear Reactor Steam Generator Tubes: Once-through steam generator tubing in certain reactor designs where the alloy's austenitic stability and moderate strength suit the design temperature range.
- Chemical Plant Piping: Transfer piping for organic and inorganic process streams in hydrogen-rich or chloride-bearing environments where iron-nickel-chromium alloys offer acceptable corrosion performance.
- Superheater and Reheater Tubing: Industrial boiler internal tubing for steam service in power plants operating at moderate superheated steam temperatures within the alloy's design limits.