# High-Temperature Corrosion Resistance of Alloy 800HT UNS N08811 in Aggressive Environments
Introduction
Keyword: Alloy 800HT UNS N08811
Alloy 800HT (UNS N08811) is a high-performance nickel-iron-chromium alloy designed for applications requiring excellent resistance to high-temperature corrosion and oxidation. This material has become increasingly important in industries where components are exposed to aggressive environments at elevated temperatures.
Composition and Properties
The chemical composition of Alloy 800HT includes approximately:
- 30-35% Nickel
- 19-23% Chromium
- 0.06-0.10% Carbon
- 0.15-0.60% Aluminum
- 0.15-0.60% Titanium
- Balance Iron
This specific composition provides the alloy with its remarkable high-temperature strength and corrosion resistance properties.
Corrosion Resistance Mechanisms
Alloy 800HT demonstrates exceptional resistance to various forms of high-temperature corrosion through several mechanisms:
Oxidation Resistance
The chromium content forms a protective chromium oxide (Cr2O3) scale that acts as a barrier against further oxidation at temperatures up to 1100°C (2012°F).
Carburization Resistance
The nickel content and balanced composition help resist carburization in hydrocarbon-rich environments, making it suitable for petrochemical applications.
Sulfidation Resistance
The alloy maintains good resistance to sulfur-containing atmospheres, though performance decreases significantly above 650°C (1200°F) in highly sulfidizing conditions.
Performance in Specific Environments
Power Generation Applications
In coal-fired power plants, Alloy 800HT resists corrosion from flue gases containing sulfur compounds, chlorides, and other aggressive elements at operating temperatures.
Petrochemical Processing
The alloy performs well in steam methane reformers and ethylene pyrolysis furnaces where it encounters high temperatures and carburizing atmospheres.
Waste Incineration
Alloy 800HT components demonstrate good resistance to the complex corrosive environments found in waste-to-energy plants.
Comparison with Similar Alloys
| Property | Alloy 800HT | Alloy 800H | Alloy 600 |
|---|---|---|---|
| Maximum Service Temperature | 1100°C | 1000°C | 1150°C |
| Carburization Resistance | Excellent | Good | Fair |
| Oxidation Resistance | Excellent | Good | Excellent |
Conclusion
Alloy 800HT UNS N08811 offers superior high-temperature corrosion resistance in aggressive environments, making it a preferred material choice for demanding industrial applications. Its balanced composition provides an optimal combination of oxidation resistance, carburization resistance