# NIMONIC Alloy 90 UNS N07090: Properties and Applications

## Introduction

NIMONIC Alloy 90, also known as UNS N07090, is a high-performance nickel-chromium-cobalt alloy that offers exceptional strength and corrosion resistance at elevated temperatures. This alloy is part of the renowned NIMONIC series, which was originally developed for gas turbine applications. Today, NIMONIC Alloy 90 finds use in various demanding industries due to its unique combination of properties.

## 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): 2.0-3.0%
– Aluminum (Al): 1.0-2.0%
– Iron (Fe): ≤2.0%
– Manganese (Mn): ≤1.0%
– Silicon (Si): ≤1.0%
– Carbon (C): ≤0.13%

## Mechanical Properties

NIMONIC Alloy 90 exhibits impressive mechanical properties, especially at high temperatures:

– Tensile Strength: 950-1200 MPa (at room temperature)
– Yield Strength: 600-850 MPa (at room temperature)
– Elongation: 15-25%
– Hardness: 30-40 HRC

– 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: 1290-1350°C (2350-2460°F)
– Thermal Expansion Coefficient: 13.5 μm/m·°C (20-1000°C)
– Thermal Conductivity: 11.7 W/m·K (at 100°C)
– Electrical Resistivity: 1.25 μΩ·m

## Key Features and Advantages

NIMONIC Alloy 90 offers several notable advantages:

– Excellent high-temperature strength
– Outstanding creep resistance
– Good oxidation resistance up to 1000°C
– Superior corrosion resistance in various environments
– Good fabricability and weldability
– Long-term stability at elevated temperatures

## Heat Treatment

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

– Solution Treatment: 1080-1120°C (1975-2050°F) followed by rapid cooling
– Aging Treatment: 700-750°C (1290-1380°F) for 16 hours
– Stress Relieving: 850-900°C (1560-1650°F) for 2 hours

## Applications

NIMONIC Alloy 90 is widely used in various high-temperature applications:

### Aerospace Industry

– Turbine blades and discs
– Combustion chamber components
– Afterburner parts
– Exhaust systems

### Power Generation

– Gas turbine components
– Steam turbine blades
– High-temperature fasteners
– Heat exchanger tubes

### Industrial Applications

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

## Fabrication and Machining

Working with NIMONIC Alloy 90 requires special considerations:

– Machining: Use carbide tools with positive rake angles and adequate cooling
– Forming: Hot forming is preferred above 980°C (1800°F)
– Welding: TIG and MIG welding are suitable with matching filler metals
– Heat Treatment: Must be performed after forming to restore properties

## Comparison with Similar Alloys

NIMONIC Alloy 90 offers distinct advantages compared