# Alloy C22 UNS N06022: Properties and Applications

## Introduction to Alloy C22

Alloy C22, also known as UNS N06022, is a nickel-chromium-molybdenum-tungsten alloy designed to resist a wide range of corrosive environments. This advanced material offers exceptional resistance to both oxidizing and reducing media, making it one of the most versatile corrosion-resistant alloys available today.

## Chemical Composition

The chemical composition of Alloy C22 plays a crucial role in its performance:

– Nickel (Ni): 56% (base element)
– Chromium (Cr): 22%
– Molybdenum (Mo): 13%
– Tungsten (W): 3%
– Iron (Fe): 3% max
– Cobalt (Co): 2.5% max
– Carbon (C): 0.015% max

## Key Properties of Alloy C22

### Corrosion Resistance

Alloy C22 exhibits outstanding resistance to:
– Pitting and crevice corrosion
– Stress corrosion cracking
– Uniform attack in oxidizing and reducing environments
– Corrosion in chloride-containing solutions

### Mechanical Properties

Typical mechanical properties at room temperature:
– Tensile Strength: 690 MPa (100 ksi) min
– Yield Strength: 310 MPa (45 ksi) min
– Elongation: 45% min
– Hardness: 90 HRB max

### Thermal Properties

– Melting Range: 1325-1370°C (2420-2500°F)
– Thermal Expansion Coefficient: 12.8 μm/m·°C (20-100°C)
– Thermal Conductivity: 10.1 W/m·K (at 100°C)

## Applications of Alloy C22

Due to its exceptional properties, Alloy C22 finds applications in numerous industries:

### Chemical Processing Industry

– Reactors and pressure vessels
– Heat exchangers
– Piping systems
– Flue gas desulfurization systems

### Pharmaceutical Industry

– Reaction vessels
– Distillation columns
– Storage tanks for aggressive chemicals

### Pollution Control

– Scrubbers
– Waste treatment systems
– Stack liners

### Oil and Gas Industry

– Downhole components
– Valves and pumps
– Seawater handling systems

## Fabrication and Welding

Alloy C22 can be fabricated using standard techniques:
– Hot working: 1050-1200°C (1920-2190°F)
– Cold working: Similar to austenitic stainless steels
– Welding: Performed using matching filler metal (ERNiCrMo-10)

## Comparison with Other Nickel Alloys

Alloy C22 offers several advantages over similar alloys:

– Better resistance to localized corrosion than Alloy C276
– Superior performance in oxidizing environments compared to Alloy 625
– More versatile than Alloy B-2 in mixed acid environments

## Conclusion

Alloy C22 UNS N06022 represents a significant advancement in corrosion-resistant materials technology. Its balanced composition provides exceptional resistance to a wide variety of aggressive environments while maintaining good fabricability. These characteristics make it an excellent choice for critical applications where reliability and long service life are essential.