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Alloy X-750 (UNS N07750) Properties and Applications

Introduction to Alloy X-750

Alloy X-750, also known as UNS N07750, is a nickel-chromium alloy that is precipitation-hardenable. It is renowned for its excellent mechanical properties, high-temperature strength, and corrosion resistance. This alloy is widely used in industries that require materials capable of withstanding extreme conditions.

Chemical Composition

The chemical composition of Alloy X-750 includes:

  • Nickel (Ni): 70% minimum

  • Chromium (Cr): 14-17%

  • Iron (Fe): 5-9%

  • Niobium (Nb) + Tantalum (Ta): 0.7-1.2%

  • Aluminum (Al): 0.4-1.0%

  • Titanium (Ti): 2.25-2.75%

  • Carbon (C): 0.08% maximum

  • Manganese (Mn): 1.0% maximum

  • Silicon (Si): 0.5% maximum

  • Sulfur (S): 0.01% maximum

  • Copper (Cu): 0.5% maximum

Mechanical Properties

Alloy X-750 exhibits outstanding mechanical properties, making it suitable for demanding applications. Key mechanical properties include:

  • Tensile Strength: 1,150 MPa (167 ksi) minimum

  • Yield Strength: 690 MPa (100 ksi) minimum

  • Elongation: 25% minimum

  • Hardness: Rockwell C 35-45

Physical Properties

The physical properties of Alloy X-750 contribute to its performance in various environments:

  • Density: 8.28 g/cm³ (0.299 lb/in³)

  • Melting Point: 1,399°C (2,550°F)

  • Thermal Conductivity: 11.4 W/m·K (79 BTU·in/hr·ft²·°F)

  • Electrical Resistivity: 1.22 µΩ·m

Heat Treatment

Alloy X-750 can be heat-treated to enhance its mechanical properties. Common heat treatment processes include:

  • Solution Annealing: 1,150-1,200°C (2,100-2,200°F) followed by rapid cooling

  • Aging: 705-760°C (1,300-1,400°F) for 16-20 hours, followed by air cooling

Corrosion Resistance

Alloy X-750 offers excellent resistance to oxidation and corrosion in various environments, including:

  • High-temperature oxidation

  • Stress-corrosion cracking

  • Corrosion in acidic and alkaline solutions

Applications of Alloy X-750

Due to its exceptional properties, Alloy X-750 is used in

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