Alloy A286 (UNS S66286) – High-Strength Superalloy for Aerospace Applications

# Alloy A286 (UNS S66286) – High-Strength Superalloy for Aerospace Applications

## Introduction to Alloy A286

Alloy A286, also known by its UNS designation S66286, is a high-strength iron-nickel-chromium superalloy that has become indispensable in aerospace applications. This precipitation-hardenable alloy combines excellent mechanical properties with good corrosion resistance, making it ideal for demanding environments.

## Composition and Properties

The chemical composition of Alloy A286 includes:

– Iron (Fe): Balance
– Nickel (Ni): 24-27%
– Chromium (Cr): 13.5-16%
– Molybdenum (Mo): 1.0-1.5%
– Titanium (Ti): 1.9-2.35%
– Aluminum (Al): 0.35% max
– Carbon (C): 0.08% max

This unique combination of elements gives Alloy A286 its remarkable properties:

– High strength at elevated temperatures (up to 1300°F/704°C)
– Excellent creep resistance
– Good oxidation resistance
– Superior fatigue strength
– Good fabricability and weldability

## Heat Treatment and Processing

Alloy A286 achieves its optimal properties through proper heat treatment:

The standard heat treatment consists of solution annealing at 1800°F (982°C) followed by rapid cooling, then aging at 1325°F (718°C) for 16 hours and air cooling. This treatment produces a fine gamma prime (γ’) precipitation throughout the matrix, responsible for the alloy’s high strength.

## Aerospace Applications

Alloy A286 finds extensive use in aerospace components due to its exceptional performance:

– Jet engine components (turbine blades, discs, and shafts)
– Afterburner parts
– Fasteners and bolts
– Structural components in high-temperature areas
– Rocket motor cases

## Advantages Over Other Alloys

Compared to other high-temperature alloys, Alloy A286 offers several advantages:

– Better strength-to-weight ratio than many stainless steels
– More cost-effective than nickel-base superalloys
– Excellent combination of strength and ductility
– Good resistance to thermal fatigue
– Maintains properties after prolonged exposure to high temperatures

## Fabrication and Machining

While Alloy A286 can be fabricated using standard methods, some considerations apply:

Machining should be performed in the annealed condition using rigid setups and positive rake tools. Welding is generally performed using matching filler metal, with post-weld heat treatment recommended for maximum properties. Cold working is possible but requires subsequent heat treatment to develop full strength.

## Conclusion

Alloy A286 (UNS S66286) remains a critical material for aerospace applications where high strength at elevated temperatures is required. Its unique combination of properties, relatively lower cost compared to nickel-base superalloys, and proven performance make it a preferred choice for numerous critical components in jet engines and spacecraft. As aerospace technology continues to advance, Alloy A286 will likely maintain its important role in enabling these technological achievements.