# 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 corrosion resistance. This superalloy has become a critical material in industries requiring components to withstand extreme environments while maintaining structural integrity.

## Chemical Composition

The unique properties of Alloy 90 stem from its carefully balanced chemical composition:

– Nickel (Ni): 55-60%
– Chromium (Cr): 18-21%
– Cobalt (Co): 15-21%
– Molybdenum (Mo): 3-5%
– Titanium (Ti): 2.5-3.5%
– Aluminum (Al): 1.2-1.8%
– Iron (Fe): ≤2.0%
– Carbon (C): ≤0.08%
– Boron (B): ≤0.015%
– Zirconium (Zr): ≤0.07%

## Mechanical Properties

Alloy 90 demonstrates impressive mechanical characteristics across a wide temperature range:

– Tensile Strength: 1200-1400 MPa (at room temperature)
– Yield Strength: 800-1000 MPa (at room temperature)
– Elongation: 15-25%
– Hardness: 30-40 HRC
– Creep Resistance: Excellent up to 980°C (1800°F)
– Fatigue Strength: Superior to most nickel-based alloys

## Physical Properties

The physical characteristics of Alloy 90 include:

– Density: 8.19 g/cm³
– Melting Range: 1290-1345°C (2350-2450°F)
– Thermal Expansion Coefficient: 13.5 μm/m·°C (20-1000°C)
– Thermal Conductivity: 11.4 W/m·K (at 100°C)
– Electrical Resistivity: 1.25 μΩ·m (at 20°C)

## Key Advantages

Alloy 90 offers several distinct advantages over other high-temperature alloys:

– Exceptional oxidation resistance up to 1100°C (2010°F)
– Superior creep-rupture strength
– Excellent thermal fatigue resistance
– Good fabricability and weldability
– Resistance to carburization and sulfidation
– Long-term microstructural stability

## Common Applications

Due to its remarkable properties, Alloy 90 finds use in numerous demanding applications:

### Aerospace Industry

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

### Power Generation

– Gas turbine components
– Heat exchangers
– Steam turbine blades
– Nuclear reactor parts

### Industrial Processing

– Furnace components
– Heat treatment fixtures
– Chemical processing equipment
– Petrochemical reactors

## Fabrication and Processing

Alloy 90 can be processed using standard techniques with some special considerations:

### Machining

Requires rigid setups and positive rake tools with adequate cooling. Carbide tools are recommended for optimal results.

### Welding

Can be welded using TIG, MIG, and resistance welding methods. Post-weld heat treatment is often necessary to restore properties.

### Heat Treatment

Solution annealing at 1080-1120°C (1975-2050°F) followed by rapid cooling is standard. Aging treatments between 700-850°C (1290-1560°F) develop optimal properties.

## Comparison with Similar Alloys

Alloy 90 offers several advantages over comparable materials:

– Higher creep strength than Inconel 718
– Better oxidation resistance than Waspaloy
– Superior thermal stability compared to Rene 41
– More cost-effective than single crystal superalloys for many applications

## Maintenance and Service Life