1. Basic Information
- Grade: Incoloy 800 / 800H / 800HT
- UNS:
- 800: N08800
- 800H: N08810
- 800HT: N08811
- W.Nr.:
- 800: 1.4876
- 800H: 1.4958
- 800HT: 1.4959
- Alloy Type: Nickel‑iron‑chromium (Ni‑Fe‑Cr) austenitic solid‑solution strengthened alloy
- Key Characteristics: Excellent high‑temperature oxidation and carburization resistance, good creep and stress‑rupture strength at elevated temperatures, superior chloride stress‑corrosion cracking (SCC) resistance. 800H and 800HT are optimized for high‑temperature structural applications between 593–982°C, while 800HT provides the highest creep strength among the three grades.
2. Chemical Composition (wt%, typical)
| Element | Incoloy 800 (N08800) | Incoloy 800H (N08810) | Incoloy 800HT (N08811) |
|---|---|---|---|
| Nickel (Ni) | 30.0–35.0 | 30.0–35.0 | 30.0–35.0 |
| Chromium (Cr) | 19.0–23.0 | 19.0–23.0 | 19.0–23.0 |
| Iron (Fe) | Balance | Balance | Balance |
| Carbon (C) | ≤0.10 | 0.05–0.10 | 0.06–0.10 |
| Aluminum (Al) | 0.15–0.60 | 0.15–0.60 | 0.25–0.60 |
| Titanium (Ti) | 0.15–0.60 | 0.15–0.60 | 0.25–0.60 |
| Al+Ti | 0.30–1.20 | 0.30–1.20 | 0.85–1.20 |
| Manganese (Mn) | ≤1.5 | ≤1.5 | ≤1.5 |
| Silicon (Si) | ≤1.0 | ≤1.0 | ≤1.0 |
| Copper (Cu) | ≤0.75 | ≤0.75 | ≤0.75 |
| Sulfur (S) | ≤0.015 | ≤0.015 | ≤0.015 |
| Phosphorus (P) | ≤0.030 | ≤0.030 | ≤0.030 |
3. Mechanical Properties (Solution Annealed Condition, Room Temperature)
| Property | Incoloy 800 | Incoloy 800H | Incoloy 800HT |
|---|---|---|---|
| Tensile Strength | ≥450 MPa | ≥490 MPa | ≥490 MPa |
| Yield Strength (0.2% offset) | ≥205 MPa | ≥275 MPa | ≥275 MPa |
| Elongation | ≥30% | ≥30% | ≥30% |
| Hardness (HRB) | 70–90 | 75–95 | 75–95 |
| Modulus of Elasticity | ~206 GPa | ~206 GPa | ~206 GPa |
High‑temperature creep and rupture performance: 800 is suitable for service up to approximately 593°C. 800H offers excellent performance from 593–982°C. 800HT provides superior creep strength above 650°C compared to 800H.
4. Corrosion & High-Temperature Resistance
General corrosion properties include excellent resistance to oxidizing and non‑oxidizing acids, salts, and alkaline solutions, outstanding resistance to chloride‑induced stress corrosion cracking (SCC), and good performance in nitric acid, organic acids such as acetic and formic acid, and sour gas environments.
High‑temperature properties feature oxidation resistance up to 1100°C in air with a protective chromium oxide film, excellent carburization resistance in carbon‑rich atmospheres, good nitriding resistance in nitrogen‑containing environments, and high thermal stability that resists sigma‑phase embrittlement, with 800HT demonstrating the best thermal stability.
5. Physical Properties
Density: 8.0 g/cm³
Melting Range: 1350–1400°C
Coefficient of Thermal Expansion (20–100°C): ~13.0 × 10⁻⁶ /°C
Thermal Conductivity (20°C): ~13.0 W/(m·K)
Electrical Resistivity (20°C): ~0.90 μΩ·m
Magnetism: Non‑magnetic
6. Fabrication & Heat Treatment
Solution annealing for Incoloy 800 is performed at 925–1010°C followed by rapid cooling. For 800H and 800HT, annealing is done at 1149–1177°C with water quenching or rapid air cooling to achieve a coarse grain size of ASTM 5 or coarser. The alloy is solid‑solution strengthened only and does not undergo age hardening.
Weldability is good using matching filler metals including ERNiCr‑3 for GTAW/GMAW and ENiCrFe‑3 for SMAW. Post‑weld annealing is recommended for 800H and 800HT to restore creep properties.
The alloy shows good cold and hot formability, with intermediate annealing potentially required for severe cold forming operations.
7. Standards & Specifications
ASTM: B409 (plate/sheet), B514/B515 (pipe/tube), B564 (forgings), B572 (bar/rod)
ASME: SB409, SB514, SB515, SB564, SB572
EN: 1.4876 (800), 1.4958 (800H), 1.4959 (800HT)
NACE: MR0175 / ISO 15156 (sour service)
8. Typical Applications
Heat treatment equipment such as furnace components, muffles, retorts, and baskets. Petrochemical applications including catalyst tubes, reformer tubes, piping, and heat exchangers. Power generation components like superheater tubes and boiler parts. Chemical processing equipment including reactors, valves, pumps, and sulfur recovery units. Industrial uses in carburizing furnaces, nitriding equipment, and thermal oxidizers.
9. Short Description (for Post List Excerpt)
Incoloy 800/800H/800HT (UNS N08800/N08810/N08811) are nickel‑iron‑chromium alloys offering exceptional high‑temperature oxidation, carburization, and creep resistance. 800H and 800HT are optimized for elevated‑temperature structural applications from 593–982°C, with 800HT delivering the highest creep strength. They are widely used in furnace, petrochemical, power generation, and chemical processing equipment.