Incoloy 800H
High-temperature austenitic alloy for creep-resistant applications up to 2100°F
Incoloy 800H delivers exceptional creep resistance and thermal fatigue strength for high-temperature furnace applications, petrochemical reactors, and aerospace engines. The controlled carbide precipitation structure provides superior strength retention at elevated temperatures while maintaining excellent oxidation and corrosion resistance.
Quick Specifications
- Density
- 8.06 g/cm³ (0.291 lb/in³)
- Melting Point
- 2500-2600°F (1370-1425°C)
- Yield Strength (0.2% offset)
- 45-50 ksi (310-345 MPa) at room temperature
- Tensile Strength
- 75-90 ksi (517-620 MPa) at room temperature
- Elongation
- 35-40% in 2 inches
- Modulus of Elasticity
- 28.4 × 10⁶ psi (195 GPa) at 70°F
Standards & Certifications
Product Description
Incoloy 800H is a registered trademark iron-nickel-chromium austenitic alloy specifically engineered for applications requiring sustained exposure to temperatures exceeding 1800°F. The 'H' designation indicates enhanced creep rupture strength through careful control of carbon and aluminum content, which promotes the formation of M₂₃C₆ carbides that anchor grain boundaries and resist creep deformation. This metallurgical refinement makes Incoloy 800H the material of choice when traditional stainless steels fail to provide adequate strength retention and when weight-optimized designs demand maximum strength-to-weight ratios.
The microstructure of Incoloy 800H consists of a stable austenitic matrix strengthened by discrete carbide precipitates at grain boundaries. Unlike conventional austenitic stainless steels that rely primarily on solid-solution strengthening, the controlled precipitation of carbides in Incoloy 800H provides additional strengthening mechanisms that maintain yield strength above 1600°F—a temperature where most austenitic stainless steels lose structural integrity. The alloy resists sigma phase embrittlement that plagues some superalloys, making it suitable for both intermittent and continuous high-temperature service.
Incoloy 800H exhibits outstanding resistance to oxidation, carburization, and sulfidation in high-temperature gas environments encountered in catalytic crackers, reformers, and furnace tubes. The chromium-rich oxide scale that forms on the surface provides excellent protection against further oxidation, even in cyclic heating and cooling conditions. This exceptional thermal fatigue resistance makes the alloy ideal for equipment experiencing rapid temperature fluctuations, such as heat exchanger tubes and furnace ducting where repeated thermal cycling would cause premature failure of less robust materials.
The combination of creep resistance, oxidation resistance, and fabricability makes Incoloy 800H invaluable in refinery operations, chemical processing, and aerospace applications. Superior weldability and formability compared to less ductile high-temperature alloys simplify manufacturing and reduce fabrication costs. The alloy's proven track record across decades of industrial service, with extensive documentation of long-term performance data, makes it the preferred choice for mission-critical high-temperature equipment where reliability and predictability are paramount.
Specifications
| Density | 8.06 g/cm³ (0.291 lb/in³) |
| Melting Point | 2500-2600°F (1370-1425°C) |
| Yield Strength (0.2% offset) | 45-50 ksi (310-345 MPa) at room temperature |
| Tensile Strength | 75-90 ksi (517-620 MPa) at room temperature |
| Elongation | 35-40% in 2 inches |
| Modulus of Elasticity | 28.4 × 10⁶ psi (195 GPa) at 70°F |
| Thermal Conductivity | 6.5 BTU/hr·ft·°F at 212°F (11.2 W/m·K) |
| Coefficient of Thermal Expansion | 7.9 × 10⁻⁶ in/in·°F (14.2 × 10⁻⁶ m/m·°C) 68-212°F |
| Creep Rupture Strength | 5 ksi (34.5 MPa) at 2000°F for 10,000 hours |
| Hardness (Annealed) | ≤ 187 HB |
Chemical Composition
| Element | Content (%) |
|---|---|
| Nickel (Ni) | 30.0-35.0 |
| Iron (Fe) | Balance |
| Chromium (Cr) | 19.0-23.0 |
| Aluminum (Al) | 0.75-1.35 |
| Titanium (Ti) | 0.15-0.60 |
| Manganese (Mn) | 1.0-2.0 |
| Silicon (Si) | 1.0-1.5 |
| Carbon (C) | 0.05-0.10 |
| Copper (Cu) | 0.0-0.5 |
| Sulfur (S) | ≤ 0.015 |
| Phosphorus (P) | ≤ 0.030 |
Mechanical Properties
| Property | Value |
|---|---|
| Yield Strength @ 70°F | 45-50 ksi (310-345 MPa) |
| Tensile Strength @ 70°F | 75-90 ksi (517-620 MPa) |
| Elongation (2 inch gauge) | 35-40% |
| Reduction of Area | 50-60% |
| Rockwell Hardness (B scale) | 85-95 HRB |
| Stress Rupture Strength (10,000 hrs @ 2000°F) | 5 ksi (34.5 MPa) |
| 1% Creep Strength (10,000 hrs @ 2000°F) | 8 ksi (55 MPa) |
| Thermal Fatigue Resistance (ΔT = 1000°F cycles) | Excellent - capable of >10,000 cycles without failure |
Key Features & Advantages
Applications
Petrochemical Reformer and Cracker Tubes
Furnace tubes in catalytic crackers and reformer furnaces operate under some of the most severe service conditions in the refining industry. Incoloy 800H withstands sustained temperatures up to 2050°F, carburizing atmospheres rich in hydrogen and hydrocarbons, and internal pressure while maintaining adequate creep strength. The alloy's resistance to coking and carburization extends tube life and reduces maintenance downtime.
Aerospace Engine Afterburner Components
Afterburner liners, exhaust ducts, and thermal protection systems in military and commercial aircraft engines. The combination of high-temperature strength, thermal fatigue resistance, and light weight makes Incoloy 800H ideal for components experiencing temperatures to 2000°F and rapid thermal cycling during engine acceleration and deceleration.
Industrial Furnace Ducting and Fans
Heat exchanger tubing, furnace ducting, and fan housings in industrial furnaces and kilns. Incoloy 800H provides the strength and oxidation resistance needed for sustained exposure to furnace atmosphere while maintaining structural integrity during thermal cycling as furnaces heat up and cool down.
Power Generation Superheater Tubes
Main and reheat superheater tubes in fossil-fueled power plants operating at elevated steam temperatures. The creep strength enables higher steam temperatures and improved thermal efficiency compared to conventional stainless steels, while oxidation resistance ensures reliable performance across the design lifetime.
Chemical Reactor Vessels and Coils
High-temperature, pressure-containing equipment in chemical manufacturing requiring sustained exposure above 1800°F. Incoloy 800H's excellent fabricability permits economical construction of complex geometries while delivering the strength and corrosion resistance essential for hazardous chemical processes.
Thermal Test Fixtures and Equipment
Furnace elements, heat shields, and test rigs in materials research and hypersonic testing facilities. The alloy's stability at extreme temperatures and excellent thermal cycling capability make it ideal for equipment that must withstand severe thermal stresses while maintaining tight tolerances.
Frequently Asked Questions
What is the maximum continuous service temperature for Incoloy 800H?
Does Incoloy 800H require post-weld heat treatment?
How does Incoloy 800H perform in cyclic thermal loading?
What precautions are necessary to prevent carburization in furnace tube applications?
Can Incoloy 800H be used in corrosive chemical environments?
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