Excellent High-Temperature and Corrosion Resistance of Incoloy 800
Incoloy 800 is a Fe-Ni-Cr alloy with excellent oxidation resistance and carburization resistance, capable of maintaining structural stability at elevated temperatures. It is widely used in heat treatment equipment, petrochemical heaters, steam generator systems, and nuclear power components—making it a preferred alloy for high-temperature structural applications.
What is Incoloy 800?
Incoloy 800 (UNS N08800) is an iron-based alloy containing a high proportion of nickel (30–35%) and chromium (19–23%), designed to maintain strength and oxidation resistance in high-temperature environments. It retains an austenitic structure between 600–1100 °C and offers excellent resistance to high-temperature corrosion, creep, and stress corrosion cracking.
Incoloy 800 Equivalent Grades
| Standard System | Equivalent Grade |
| UNS | N08800 |
| W.Nr. | 1.4876 |
| ASTM | B409 / B408 / B564 / B407 |
| JIS | NCF800 |
| ISO / EN | X10NiCrAlTi32-20 |
Incoloy 800 Chemical Composition (Typical Range)
| Element | Content (%) |
| Nickel (Ni) | 30.0 – 35.0 |
| Chromium (Cr) | 19.0 – 23.0 |
| Iron (Fe) | Balance |
| Carbon (C) | ≤ 0.10 |
| Aluminum (Al) | 0.15 – 0.60 |
| Titanium (Ti) | 0.15 – 0.60 |
| Manganese (Mn) | ≤ 1.5 |
| Silicon (Si) | ≤ 1.0 |
| Sulfur (S) | ≤ 0.015 |
| Copper (Cu) | ≤ 0.75 |
Incoloy 800 Mechanical Properties (Annealed, Room Temperature)
| Property | Typical Value |
| Tensile Strength | ≥ 450 MPa |
| Yield Strength (0.2%) | ≥ 170 MPa |
| Elongation | ≥ 30% |
| Brinell Hardness | ≤ 200 HB |
Incoloy 800 Physical Properties
| Property | Value |
| Density | 7.94 g/cm³ |
| Melting Point Range | 1357 – 1385 °C |
| Thermal Conductivity (RT) | ~11.3 W/m·K |
| Electrical Resistivity | ~1.12 μΩ·m |
| Specific Heat | 0.42 J/g·K |
| Magnetic Properties | Non-magnetic (Austenitic) |
Applications of Incoloy 800
- Petrochemical furnace piping and reheater systems
- Heat treatment furnaces, annealing furnaces, and their components (hangers, trays, tubes)
- Chemical processing heat exchangers and reactor structures
- High-temperature steam generators and pressure vessels
- Structural components in nuclear power systems
- Aerospace engine parts and fasteners used in high-temperature environments
Advantages of Incoloy 800
- Exceptional structural stability in high-temperature (600–1100 °C) environments
- Excellent oxidation and carburization resistance
- Good creep-rupture strength at elevated temperatures
- Strong resistance to stress corrosion cracking (SCC) in moderate chloride environments
- Good processability and weldability, suitable for hot and cold forming
Limitations of Incoloy 800
- Not suitable for strong reducing acids such as hydrochloric acid
- Welding heat input must be controlled at high temperatures to avoid grain coarsening
- Less pitting resistance in chloride-rich environments compared to high-performance nickel alloys like C276
- Higher cost than stainless steels
Incoloy 800 vs. Incoloy 800H vs. Incoloy 800HT
- Incoloy 800: The base version, suitable for general high-temperature corrosion and oxidation resistance.
- Incoloy 800H: Designed for enhanced creep resistance, thanks to controlled carbon and coarser grain size.
- Incoloy 800HT: Offers maximum creep rupture strength, with tighter control of (Al + Ti) and heat treatment, making it ideal for prolonged exposure to extreme temperatures.
| Property / Feature | Incoloy 800 | Incoloy 800H | Incoloy 800HT |
| UNS Number | N08800 | N08810 | 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% |
| Carbon (C) | ≤ 0.10% | 0.05–0.10% | 0.06–0.10% |
| Aluminum + Titanium | No strict control | Ti: 0.15–0.60%, Al: 0.15–0.60% | (Al + Ti): 0.85–1.20% (strictly controlled) |
| Grain Size | Not controlled | ASTM No. 5 or coarser | ASTM No. 5 or coarser |
| Creep & Rupture Strength | Moderate | Improved | Highest |
| Heat Treatment | Annealed | Solution annealed | Solution annealed with stricter Al+Ti control |
| Max Service Temp (typical) | ~1100°C (2012°F) | ~1100–1150°C (2012–2100°F) | ~1150°C (2100°F) |
| ASME Code Use | Limited | Approved for high-temperature use | Preferred for long-term creep resistance |
| Typical Applications | Heat exchangers, vessels | Furnace components, reformers | Superheaters, petrochemical processing |
FAQ About Incoloy 800
Suitable for long-term service up to 1100 °C. Higher temperatures are possible for short durations but must consider strength loss and oxidation.
Yes. It has good weldability using matching filler metals like ERNiCr-3, with controlled heat input to avoid hot cracking or grain growth.
No, it’s not ideal for seawater or strong acidic media. Alloys like Inconel 625 or Hastelloy C276 are better suited for such conditions.
Summary
This article introduces Incoloy 800, explains the alloy, and discusses its composition, properties, and applications. For more information about Incoloy 800, please get in touch with an MT.BOLTS representative.
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