# Alloy 90 UNS N07090: Properties and Applications

## Introduction to Alloy 90 UNS N07090

Alloy 90, also known as UNS N07090, is a nickel-chromium-cobalt alloy that offers exceptional high-temperature strength and oxidation resistance. This superalloy is widely used in demanding applications where performance under extreme conditions is critical.

## Chemical Composition

The chemical composition of Alloy 90 plays a crucial role in its performance characteristics:

– Nickel (Ni): 58-63%
– Chromium (Cr): 18-21%
– Cobalt (Co): 15-21%
– Molybdenum (Mo): 3-5%
– Aluminum (Al): 1.0-2.0%
– Titanium (Ti): 2.5-3.5%
– Iron (Fe): ≤2.0%
– Carbon (C): ≤0.10%
– Manganese (Mn): ≤1.0%
– Silicon (Si): ≤1.0%

## Mechanical Properties

Alloy 90 exhibits impressive mechanical properties across a wide temperature range:

– Tensile Strength: 1200-1400 MPa at room temperature
– Yield Strength: 800-1000 MPa at room temperature
– Elongation: 15-25% at room temperature
– Creep Resistance: Excellent performance up to 980°C (1800°F)
– Fatigue Strength: Superior resistance to cyclic loading

## Physical Properties

The physical characteristics of Alloy 90 include:

– Density: 8.19 g/cm³
– Melting Range: 1290-1350°C (2350-2460°F)
– Thermal Expansion Coefficient: 12.6 × 10⁻6/°C (20-1000°C)

– Thermal Conductivity: 11.4 W/m·K at 20°C
– Electrical Resistivity: 1.25 μΩ·m at 20°C

## Key Advantages

Alloy 90 offers several distinct advantages that make it suitable for demanding applications:

– Exceptional high-temperature strength
– Outstanding oxidation resistance up to 1095°C (2000°F)
– Good resistance to thermal fatigue
– Excellent creep-rupture properties
– Maintains mechanical properties after prolonged exposure to high temperatures

## Common Applications

Alloy 90 finds use in numerous high-performance applications:

### Aerospace Industry

– Turbine blades and vanes
– Combustion chambers
– Afterburner components
– Exhaust systems

### Power Generation

– Gas turbine components
– Heat exchangers
– High-temperature fasteners
– Steam turbine parts

### Industrial Applications

– Furnace components
– Heat treatment equipment
– Chemical processing equipment
– Nuclear reactor components

## Fabrication and Processing

Working with Alloy 90 requires special considerations:

### Machining

– Use rigid machine setups
– Employ positive rake tools
– Maintain sharp cutting edges
– Use heavy-duty coolant systems

### Welding

– Recommended methods: GTAW, GMAW, PAW
– Use matching filler metals
– Pre-weld and post-weld heat treatment may be required
– Control interpass temperatures

### Heat Treatment

– Solution treatment: 1080-1120°C (1975-2050°F)
– Aging treatment: 700-800°C (1290-1470°F)
– Stress relief annealing available

## Comparison with Other Superalloys

Alloy 90 offers a unique combination of properties compared to similar materials:

– Higher creep strength than Alloy 718 at temperatures above 650°C (1200°F)
– Better oxidation resistance than Waspaloy
– Superior thermal fatigue resistance compared to Rene 41
– More cost-effective than single-crystal superalloys for many applications