# Alloy 800 (UNS N08800) Properties and Applications
## Introduction to Alloy 800
Alloy 800, also known as UNS N08800, is a nickel-iron-chromium alloy with excellent resistance to oxidation and carburization at high temperatures. This material is widely used in various industrial applications 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%
– Copper (Cu): ≤0.75%
– Sulfur (S): ≤0.015%
## Mechanical Properties
Alloy 800 exhibits excellent mechanical properties across a wide temperature range:
### Room Temperature Properties
– Tensile Strength: 500-700 MPa
– Yield Strength: 200-350 MPa
– Elongation: 30-45%
– Hardness: 150-200 HB
### Elevated Temperature Properties
– Maintains good strength up to 815°C (1500°F)
– Excellent creep resistance
– Good fatigue properties
## Physical Properties
Key physical properties of Alloy 800 include:
– Density: 7.94 g/cm³
– Melting Range: 1350-1400°C (2460-2550°F)
– Thermal Expansion Coefficient: 14.4 μm/m·°C (20-100°C)
– Thermal Conductivity: 11.2 W/m·K (100°C)
– Electrical Resistivity: 0.98 μΩ·m
## Corrosion Resistance
Alloy 800 offers outstanding corrosion resistance in various environments:
– Excellent resistance to oxidation up to 1100°C (2010°F)
– Good resistance to carburization and sulfidation
– Performs well in nitric acid, organic acids, and alkaline solutions
Keyword: Alloy 800 UNS N08800
– Resistant to stress corrosion cracking in chloride environments
## Heat Treatment
Proper heat treatment enhances the properties of Alloy 800:
– Solution Annealing: 925-1040°C (1700-1900°F) followed by rapid cooling
– Stress Relieving: 540-650°C (1000-1200°F) for 1-2 hours
– Stabilization Annealing: 870-900°C (1600-1650°F) to improve resistance to intergranular corrosion
## Fabrication and Welding
Alloy 800 can be readily fabricated using standard techniques:
### Forming
– Hot working temperature: 870-1230°C (1600-2250°F)
– Cold working requires intermediate annealing
### Welding
– Suitable for most welding processes including TIG, MIG, and resistance welding
– Recommended filler metals: Alloy 800H or ENiCrFe-2/3
– Post-weld heat treatment may be required for critical applications
## Applications of Alloy 800
Due to its excellent properties, Alloy 800 finds applications in various industries:
### Chemical Processing
– Heat exchangers
– Reaction vessels
– Piping systems
– Catalyst support grids
### Power Generation
– Steam generator tubing
– Superheater tubes
– Heat exchanger components
### Petrochemical Industry
– Ethylene pyrolysis furnaces
– Reformer tubes
– Transfer piping
### Nuclear Industry
– Steam generator tubing in pressurized water reactors
– Heat exchanger components
### Other Applications
– Industrial heating elements
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