NIMONIC Alloy 90 UNS N07090: Properties and Applications

# NIMONIC Alloy 90 UNS N07090: Properties and Applications

## Introduction to NIMONIC Alloy 90

NIMONIC Alloy 90, also known as UNS N07090, is a high-performance nickel-chromium-cobalt alloy that exhibits excellent mechanical strength and resistance to oxidation at elevated temperatures. Developed by Rolls-Royce in the 1940s, this alloy has become a cornerstone material in industries requiring materials that can withstand extreme conditions.

## Chemical Composition

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

– Nickel (Ni): 55-60%
– Chromium (Cr): 18-21%
– Cobalt (Co): 15-21%
– Titanium (Ti): 2.0-2.8%
– Aluminum (Al): 1.0-1.8%
– Iron (Fe): ≤2.0%
– Manganese (Mn): ≤1.0%
– Silicon (Si): ≤1.0%
– Carbon (C): ≤0.13%

## Mechanical Properties

NIMONIC Alloy 90 demonstrates impressive mechanical properties across a wide temperature range:

– Tensile Strength: 950-1200 MPa at room temperature
– Yield Strength: 550-850 MPa at room temperature
– Elongation: 20-30% at room temperature
– Hardness: 250-350 HB
– Creep Resistance: Excellent up to 815°C (1500°F)

## Physical Properties

The physical characteristics of NIMONIC Alloy 90 include:

– Density: 8.19 g/cm³
– Melting Range: 1290-1345°C (2350-2450°F)
– Thermal Conductivity: 11.2 W/m·K at 20°C
– Electrical Resistivity: 1.18 μΩ·m at 20°C
– Coefficient of Thermal Expansion: 13.2 μm/m·K (20-100°C)

## Heat Treatment

Proper heat treatment is essential for optimizing the properties of NIMONIC Alloy 90:

– Solution Treatment: 1080°C (1975°F) for 8 hours, followed by air cooling
– Aging Treatment: 700°C (1290°F) for 16 hours, followed by air cooling
– Stress Relieving: 900°C (1650°F) for 4 hours, followed by air cooling

## Corrosion Resistance

NIMONIC Alloy 90 offers excellent resistance to:

– Oxidation at high temperatures
– Sulfidation
– Carburization
– Chloride-induced stress corrosion cracking
– General corrosion in many industrial environments

## Applications

Due to its exceptional properties, NIMONIC Alloy 90 finds applications in various demanding industries:

### Aerospace Industry

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

### Power Generation

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

### Industrial Applications

– High-temperature furnace components
– Chemical processing equipment
– Nuclear reactor components
– Oil and gas downhole tools

## Fabrication and Machining

Working with NIMONIC Alloy 90 requires special considerations:

### Forming

– Hot forming is preferred at 980-1150°C (1800-2100°F)
– Cold forming is possible but requires intermediate annealing

### Machining

– Use rigid machine setups
– Employ positive rake angles
– Use carbide or ceramic cutting tools
– Maintain adequate cooling and lubrication

### Welding

– Gas tungsten arc welding (GTAW) is preferred
– Use matching filler metal (NIMONIC All