# High-Temperature Performance and Applications of Alloy 800H UNS N08810

## Introduction to Alloy 800H UNS N08810

Alloy 800H (UNS N08810) is a nickel-iron-chromium alloy designed for high-temperature applications. This material is known for its excellent resistance to oxidation and carburization, making it a preferred choice for industries operating in extreme environments.

## Chemical Composition and Properties

The chemical composition of Alloy 800H includes:

– Nickel: 30-35%
– Chromium: 19-23%
– Iron: Balance
– Carbon: 0.05-0.10%
– Aluminum: 0.15-0.60%
– Titanium: 0.15-0.60%

This unique combination of elements provides the alloy with:

– Excellent high-temperature strength
– Good resistance to oxidation and carburization
– Superior creep and rupture properties
– Good fabricability and weldability

## High-Temperature Performance

Alloy 800H demonstrates exceptional performance in high-temperature environments:

### Oxidation Resistance

The alloy forms a protective chromium oxide layer at temperatures up to 1100°C (2012°F), providing excellent resistance to oxidation. This makes it suitable for applications in furnace components and heat treatment equipment.

### Creep and Rupture Strength

With controlled carbon content and stabilized titanium and aluminum additions, Alloy 800H maintains superior creep and rupture strength at elevated temperatures compared to standard Alloy 800.

### Carburization Resistance

The alloy shows remarkable resistance to carburizing environments, making it ideal for petrochemical processing equipment exposed to hydrocarbon atmospheres at high temperatures.

## Industrial Applications

Alloy 800H finds extensive use in various high-temperature applications:

### Petrochemical Industry

– Steam methane reformer tubes
– Ethylene pyrolysis furnaces
– Hydrocarbon cracking equipment

### Power Generation

– Heat exchangers
– Superheater tubes
– Boiler components

### Industrial Heating

– Radiant tubes
– Muffles
– Retorts
– Furnace fixtures

### Nuclear Applications

– Heat exchangers in nuclear reactors
– Steam generator tubing

## Fabrication and Welding Considerations

When working with Alloy 800H, several factors should be considered:

### Forming

The alloy can be readily formed using standard techniques, though it work hardens more rapidly than carbon steel. Intermediate annealing may be required for severe forming operations.

### Welding

Alloy 800H is readily weldable using common techniques:

– Gas tungsten arc welding (GTAW)
– Gas metal arc welding (GMAW)
– Shielded metal arc welding (SMAW)

Post-weld heat treatment is generally not required for thin sections, but may be beneficial for heavy sections to optimize creep resistance.

## Conclusion

Alloy 800H UNS N08810 stands out as a superior material for high-temperature applications where oxidation resistance, creep strength, and carburization resistance are critical. Its versatility across multiple industries and excellent fabrication characteristics make it a valuable engineering material for demanding service conditions.