# Alloy 263 UNS N07263: Properties and Applications

## Introduction to Alloy 263 UNS N07263

Alloy 263, also known as UNS N07263, is a nickel-chromium-cobalt-molybdenum alloy that offers excellent high-temperature strength and oxidation resistance. This superalloy is widely used in demanding applications where both mechanical properties and corrosion resistance are critical.

## Chemical Composition

The chemical composition of Alloy 263 plays a crucial role in its performance characteristics:

– Nickel (Ni): 51% (base)
– Chromium (Cr): 19-21%
– Cobalt (Co): 19-21%
– Molybdenum (Mo): 5.6-6.1%
– Titanium (Ti): 1.9-2.4%
– Aluminum (Al): 0.3-0.6%
– Carbon (C): 0.04-0.08%
– Iron (Fe): ≤0.7%
– Manganese (Mn): ≤0.6%
– Silicon (Si): ≤0.4%

## Mechanical Properties

Alloy 263 exhibits impressive mechanical properties across a wide temperature range:

### Room Temperature Properties

– Tensile Strength: 950-1200 MPa
– Yield Strength: 550-850 MPa
– Elongation: 30-50%
– Hardness: 200-250 HB

### Elevated Temperature Properties

At 700°C (1292°F):
– Tensile Strength: ~700 MPa
– Creep Rupture Strength: Excellent performance under long-term stress

## Physical Properties

The physical characteristics of Alloy 263 include:

– Density: 8.36 g/cm³
– Melting Range: 1315-1370°C (2400-2500°F)
– Thermal Expansion Coefficient: 13.5 μm/m·°C (20-1000°C)
– Thermal Conductivity: 11.2 W/m·K at 100°C
– Electrical Resistivity: 1.18 μΩ·m at 20°C

## Key Features and Advantages

Alloy 263 offers several notable advantages:

– Exceptional high-temperature strength
– Good oxidation resistance up to 1000°C (1832°F)
– Excellent creep-rupture properties
– Good fabricability and weldability
– Resistance to thermal fatigue
– Stability in long-term service

## Heat Treatment

Proper heat treatment is essential for optimizing Alloy 263’s properties:

### Solution Annealing

Typically performed at 1150°C (2100°F) followed by rapid cooling to achieve optimal mechanical properties.

### Aging Treatment

Aging at 800°C (1472°F) for 8 hours enhances precipitation hardening and improves high-temperature strength.

## Fabrication and Processing

Alloy 263 can be processed using standard techniques:

### Machining

Requires slower speeds and heavier feeds than conventional steels due to its work-hardening characteristics.

### Welding

Can be welded using gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) processes with matching filler metals.

### Forming

Hot forming is preferred, though cold forming is possible with proper annealing between operations.

## Applications of Alloy 263 UNS N07263

Alloy 263 finds use in numerous demanding applications:

### Aerospace Industry

– Combustion chambers
– Afterburner components
– Turbine casings

### Power Generation

– Gas turbine components
– Combustion liners
– Transition ducts

### Industrial Processing

– Heat treatment fixtures
– Furnace components
– Chemical processing equipment

### Oil and Gas

– Downhole tools
– High-temperature valves
– Wellhead components

## Corrosion Resistance

Alloy 263 demonstrates excellent resistance to:

– High-temperature oxidation
– Sulfidation