# Alloy 263 UNS N07263: Properties and Applications

## Introduction to Alloy 263

Alloy 263, also known as UNS N07263, is a nickel-chromium-cobalt-molybdenum alloy designed for high-temperature applications. This precipitation-hardenable superalloy offers an exceptional combination of strength, oxidation resistance, and fabricability, making it a popular choice in demanding industrial environments.

## Chemical Composition

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

– Nickel (Ni): 51% (base element)
– Chromium (Cr): 20%
– Cobalt (Co): 20%
– Molybdenum (Mo): 5.9%
– Titanium (Ti): 2.1%
– Aluminum (Al): 0.4%
– Carbon (C): 0.04-0.08%
– Boron (B): 0.005%
– Iron (Fe): ≤0.7%
– Manganese (Mn): ≤0.6%
– Silicon (Si): ≤0.4%

## Key Properties of Alloy 263

### Mechanical Properties

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

– Tensile Strength: 1,000-1,300 MPa (145-189 ksi)
– Yield Strength: 700-1,000 MPa (102-145 ksi)
– Elongation: 20-30%
– Hardness: 30-40 HRC (after heat treatment)

### Thermal Properties

The alloy maintains its strength at elevated temperatures:

– Melting Range: 1,330-1,360°C (2,426-2,480°F)
– Maximum Service Temperature: 980°C (1,800°F) for short-term exposure
– Continuous Service Temperature: 870°C (1,600°F)

### Corrosion Resistance

Alloy 263 demonstrates excellent resistance to:

– Oxidation at high temperatures
– Sulfidation
– Carburization
– Nitriding environments

## Heat Treatment

Proper heat treatment is essential to achieve optimal properties:

1. Solution Annealing: 1,150-1,200°C (2,100-2,190°F) followed by rapid cooling
2. Aging: 800°C (1,470°F) for 8 hours, air cool

## Fabrication and Machining

### Forming

Alloy 263 can be formed using standard techniques:

– Hot working: 1,040-1,200°C (1,900-2,190°F)
– Cold working: Possible but requires intermediate annealing

### Machining

Machining requires rigid setups and sharp tools:

– Use positive rake angles
– Maintain adequate coolant flow
– Employ slow speeds and heavy feeds
– Carbide tools recommended

### Welding

Alloy 263 is readily weldable using:

– Gas tungsten arc welding (GTAW)
– Gas metal arc welding (GMAW)
– Shielded metal arc welding (SMAW)

Post-weld heat treatment is recommended for critical applications.

## Applications of Alloy 263

Alloy 263 finds use in numerous high-temperature applications:

### Aerospace Industry

– Combustion chambers
– Afterburner components
– Turbine casings
– Exhaust systems

### Power Generation

– Gas turbine components
– Combustion liners
– Transition ducts
– Heat exchangers

### Industrial Processing

– Heat treatment fixtures
– Furnace components
– Chemical processing equipment

## Advantages Over Competing Alloys

Alloy 263 offers several advantages compared to similar high-temperature alloys:

– Better fabricability than many precipitation-hardened alloys
– Superior strength at intermediate temperatures (650-870°C)
– Excellent creep resistance
– Good thermal fatigue resistance
– Maintains ductility after aging