# Alloy 903 UNS N19903: Properties and Applications
## Introduction to Alloy 903 UNS N19903
Alloy 903, also known by its UNS designation N19903, is a nickel-iron-cobalt superalloy known for its excellent mechanical properties and thermal stability. This alloy is specifically designed to maintain strength and dimensional stability over a wide temperature range, making it ideal for demanding aerospace and industrial applications.
## Chemical Composition
The unique properties of Alloy 903 stem from its carefully balanced chemical composition:
– Nickel (Ni): 38-41%
– Iron (Fe): 15-20%
– Cobalt (Co): 15-20%
– Niobium (Nb): 4.7-5.5%
– Titanium (Ti): 1.3-1.7%
– Aluminum (Al): 0.7-1.2%
This combination of elements provides the alloy with its characteristic high strength and low thermal expansion properties.
## Mechanical Properties
Alloy 903 exhibits impressive mechanical characteristics:
– Tensile Strength: 1,240 MPa (180 ksi) minimum
– Yield Strength: 1,035 MPa (150 ksi) minimum
– Elongation: 12% minimum
– Hardness: 38-45 HRC
– Modulus of Elasticity: 172 GPa (25 x 10^6 psi)
These properties remain stable across a temperature range from cryogenic conditions up to about 650°C (1,200°F).
## Physical Properties
Key physical characteristics include:
– Density: 8.19 g/cm³ (0.296 lb/in³)
– Melting Range: 1,315-1,425°C (2,400-2,600°F)
– Thermal Expansion Coefficient: 5.1-8.6 μm/m·°C (2.8-4.8 μin/in·°F) from 20-650°C
– Electrical Resistivity: 1.05 μΩ·m
## Thermal Stability
One of the most notable features of Alloy 903 is its exceptional thermal stability. The alloy maintains:
– Consistent mechanical properties after prolonged exposure to high temperatures
– Minimal dimensional changes during thermal cycling
– Excellent resistance to thermal fatigue
## Corrosion Resistance
While not primarily designed as a corrosion-resistant alloy, Alloy 903 demonstrates:
– Good resistance to oxidation at elevated temperatures
– Moderate resistance to various industrial atmospheres
– Better corrosion resistance than many high-strength steels
## Fabrication and Processing
Alloy 903 can be processed using standard methods:
– Machining: Requires rigid setups and sharp tools due to work hardening
– Welding: Can be welded using TIG or resistance methods
– Heat Treatment: Typically solution treated and aged for optimal properties
– Forming: Can be cold worked but requires annealing between operations
## Primary Applications
The unique combination of properties makes Alloy 903 suitable for:
Keyword: Alloy 903 UNS N19903
### Aerospace Components
– Jet engine components
– Turbine blades and disks
– High-temperature fasteners
– Rocket motor cases
### Industrial Applications
– Precision instruments requiring dimensional stability
– High-temperature springs
– Nuclear reactor components
– Oil and gas downhole tools
## Advantages Over Other Alloys
Alloy 903 offers several benefits compared to similar materials:
– Better thermal stability than most nickel-based superalloys
– Higher strength-to-weight ratio than many alternatives
– More predictable thermal expansion characteristics
– Excellent fatigue resistance under cyclic loading
## Limitations and Considerations
While highly capable, Alloy 903 has some limitations:
– Higher cost than conventional steels
– Requires specialized machining techniques
– Limited corrosion resistance in harsh environments
– Not suitable for applications requiring extreme corrosion resistance
## Conclusion
Alloy 903 UNS N19903 represents an excellent material choice for applications demanding high strength, dimensional stability