# Nimonic 90: High-Temperature Alloy for Aerospace Applications

## Introduction to Nimonic 90

Nimonic 90 is a nickel-chromium-cobalt alloy that belongs to the family of superalloys. Developed in the mid-20th century, this material has become a cornerstone in high-temperature applications, particularly in the aerospace industry. Its exceptional combination of strength, corrosion resistance, and thermal stability makes it ideal for components exposed to extreme conditions.

## Composition and Properties

The chemical composition of Nimonic 90 typically includes:

– Nickel: ~55-60%
– Chromium: ~18-21%
– Cobalt: ~15-21%
– Titanium: ~2-3%
– Aluminum: ~1-2%

This unique blend of elements gives Nimonic 90 its remarkable properties:

– High tensile strength at elevated temperatures (up to 815°C)
– Excellent creep resistance
– Good oxidation and corrosion resistance
– Superior fatigue resistance
– Maintains mechanical properties after prolonged exposure to high temperatures

## Manufacturing and Processing

Nimonic 90 can be processed through various methods:

### Forging and Hot Working

The alloy is typically hot worked in the temperature range of 1050-1150°C. Care must be taken during cooling to prevent cracking and ensure optimal properties.

### Heat Treatment

A standard heat treatment process for Nimonic 90 includes:

1. Solution treatment at 1080°C followed by rapid cooling
2. Aging at 700-750°C for 16 hours to precipitate strengthening phases

### Machining

While machinable, Nimonic 90 requires special tooling and techniques due to its high strength and work-hardening characteristics.

## Aerospace Applications

Nimonic 90 finds extensive use in critical aerospace components:

### Turbine Components

– Turbine blades
– Discs
– Shafts
– Seals

### Combustion Systems

– Combustion chambers
– Afterburner components
– Exhaust systems

### Other Critical Parts

– Fasteners
– Bearings
– High-temperature springs

## Advantages Over Other Alloys

Compared to similar high-temperature alloys, Nimonic 90 offers:

– Better creep resistance than many stainless steels
– Higher temperature capability than titanium alloys
– Superior oxidation resistance compared to cobalt-based alloys

– More cost-effective than some nickel-based superalloys for certain applications

## Future Developments

Research continues to enhance Nimonic 90’s capabilities:

– Improved coating technologies for better oxidation resistance
– Advanced manufacturing techniques like additive manufacturing
– Alloy modifications for specific applications
– Development of joining techniques for complex assemblies

## Conclusion

Nimonic 90 remains a vital material in aerospace engineering, offering an optimal balance of properties for high-temperature applications. Its continued development ensures it will remain relevant as aerospace technology advances toward higher performance and efficiency requirements.