# Alloy 690 UNS N06690: Properties and Applications in High-Temperature Environments

Introduction to Alloy 690 UNS N06690

Alloy 690 UNS N06690 is a nickel-chromium-iron alloy that has gained significant attention in industries requiring materials with excellent resistance to high temperatures and corrosive environments. This advanced material offers superior performance compared to many other alloys, making it a preferred choice for critical applications.

Chemical Composition

The composition of Alloy 690 is carefully balanced to achieve its remarkable properties:

• Nickel (Ni): 58-63%
• Chromium (Cr): 27-31%
• Iron (Fe): 7-11%
• Carbon (C): 0.05% max
• Manganese (Mn): 0.50% max
• Silicon (Si): 0.50% max
• Copper (Cu): 0.50% max
• Sulfur (S): 0.015% max

Key Properties of Alloy 690

High-Temperature Resistance

Alloy 690 maintains excellent mechanical properties at elevated temperatures, making it suitable for applications in extreme heat environments. Its high chromium content provides outstanding oxidation resistance at temperatures up to 1200°C (2192°F).

Corrosion Resistance

The alloy demonstrates exceptional resistance to:

• Oxidizing and reducing acids
• Chloride-induced stress corrosion cracking
• Intergranular attack
• Pitting and crevice corrosion

Mechanical Properties

Typical mechanical properties at room temperature include:

• Tensile strength: 550-690 MPa
• Yield strength: 240-310 MPa
• Elongation: 30-45%

Applications in High-Temperature Environments

Nuclear Industry

Alloy 690 is extensively used in nuclear power plants for:

• Steam generator tubing
• Reactor vessel internals
• Control rod drive mechanisms

Chemical Processing

The alloy finds applications in:

• High-temperature chemical reactors
• Furnace components
• Heat exchangers

Aerospace Industry

Alloy 690 is utilized in:

• Jet engine components
• Exhaust systems
• High-temperature fasteners

Fabrication and Welding

Alloy 690 can be readily fabricated using standard techniques, though it requires more power than austenitic stainless steels due to its higher strength. Recommended welding methods include:

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

Conclusion

Alloy 690 UNS N06690 stands out as a high-performance material for demanding applications in extreme environments. Its combination of high-temperature strength, corrosion resistance, and fabricability makes it invaluable across multiple industries, particularly where reliability and longevity are critical factors.</