# Alloy 800 UNS N08800: Properties and Applications

## Introduction to Alloy 800 UNS N08800

Alloy 800, also known as UNS N08800, is a nickel-iron-chromium alloy that offers excellent resistance to oxidation and carburization at high temperatures. This material is widely used in various industries due to its unique combination of mechanical properties and corrosion resistance.

## Chemical Composition

The chemical composition of Alloy 800 plays a crucial role in its performance:

– Nickel (Ni): 30-35%
– Chromium (Cr): 19-23%
– Iron (Fe): Balance
– Carbon (C): ≤ 0.10%
– Manganese (Mn): ≤ 1.5%
– Silicon (Si): ≤ 1.0%
– Aluminum (Al): 0.15-0.60%
– Titanium (Ti): 0.15-0.60%

## Mechanical Properties

Alloy 800 exhibits impressive mechanical properties across a wide temperature range:

Property | Value
Tensile Strength | 500-700 MPa
Yield Strength | 200-400 MPa
Elongation | 30-45%
Hardness (Rockwell B) | 70-90

## Physical Properties

The physical characteristics of Alloy 800 include:

– Density: 7.94 g/cm³
– Melting Range: 1350-1400°C (2462-2552°F)
– Thermal Conductivity: 11.2 W/m·K at 100°C
– Electrical Resistivity: 0.98 μΩ·m at 20°C

## Corrosion Resistance

Alloy 800 demonstrates excellent resistance to various corrosive environments:

– Oxidation resistance up to 1100°C (2012°F)
– Resistance to carburizing and nitriding atmospheres
– Good performance in sulfur-containing environments
– Resistance to chloride stress corrosion cracking

## Heat Treatment

Proper heat treatment enhances the properties of Alloy 800:

– Solution annealing: 925-1040°C (1697-1904°F) followed by rapid cooling
– Stress relieving: 540-650°C (1004-1202°F) for 1-2 hours

## Applications of Alloy 800

Alloy 800 finds applications in numerous industries:

### 1. Chemical Processing

– Heat exchangers
– Reaction vessels
– Piping systems

### 2. Power Generation

– Steam generator tubing
– Superheater tubes
– Nuclear reactor components

### 3. Petrochemical Industry

– Furnace components
– Catalytic reforming systems
– Hydrocarbon cracking equipment

### 4. Heat Treating Industry

– Retorts
– Muffles
– Trays and fixtures

## Advantages of Alloy 800

The key benefits of using Alloy 800 include:

– Excellent high-temperature strength
– Good creep-rupture properties
– Resistance to oxidation and carburization
– Good fabricability and weldability
– Long service life in demanding environments

## Fabrication and Welding

Alloy 800 can be readily fabricated using standard techniques:

– Hot working: 870-1230°C (1600-2250°F)
– Cold working: Requires intermediate annealing
– Welding: Can be welded using GTAW, GMAW, and SMAW processes

## Conclusion

Alloy 800 UNS N08800 is a versatile material that combines excellent high-temperature properties with good corrosion resistance. Its unique composition makes it suitable for demanding applications across various industries, particularly where resistance to oxidation and carburization is required. The alloy’s mechanical properties, fabricability, and long-term performance make it a preferred choice for critical components in harsh environments.