# Stellite12 Alloy UNS R30012 Properties and Applications

## Introduction to Stellite12 Alloy

Stellite12 is a cobalt-based alloy that belongs to the Stellite family of superalloys. Designated as UNS R30012, this alloy is known for its excellent wear resistance, high-temperature strength, and corrosion resistance properties. It finds extensive use in demanding industrial applications where durability and performance are critical.

## Chemical Composition of Stellite12

The unique properties of Stellite12 alloy stem from its carefully balanced chemical composition:

– Cobalt (Co): 50-55%
– Chromium (Cr): 28-32%
– Tungsten (W): 7-9.5%
– Carbon (C): 1-1.4%
– Nickel (Ni): 2-4%
– Iron (Fe): ≤3%
– Silicon (Si): ≤1%
– Manganese (Mn): ≤1%

## Mechanical Properties

Stellite12 exhibits impressive mechanical characteristics:

– Hardness: 38-45 HRC (Rockwell C scale)
– Tensile Strength: 1000-1200 MPa
– Yield Strength: 700-850 MPa
– Elongation: 2-5%
– Density: 8.4 g/cm³

## Physical Properties

Key physical properties of Stellite12 include:

– Melting Point: 1290-1350°C (2354-2462°F)
– Thermal Conductivity: 14.6 W/m·K
– Coefficient of Thermal Expansion: 12.3 × 10⁻⁶/°C (20-100°C)
– Electrical Resistivity: 0.92 μΩ·m

## Corrosion Resistance

Stellite12 demonstrates excellent corrosion resistance in various environments:

– Outstanding resistance to oxidizing acids
– Good performance in reducing media
– Excellent resistance to seawater and salt spray
– Maintains integrity in high-temperature corrosive environments

## Wear Resistance

The alloy’s wear resistance characteristics include:

– Superior abrasion resistance
– Excellent galling resistance
– Good erosion resistance
– Maintains hardness at elevated temperatures

## Heat Treatment

Stellite12 typically does not require heat treatment for hardening as it achieves its properties through solid solution strengthening and carbide precipitation. However, stress relief annealing can be performed at 760-790°C (1400-1450°F) for 1-2 hours followed by air cooling.

## Fabrication and Machining

Processing considerations for Stellite12:

– Can be cast using investment casting methods
– Machinable in annealed condition using carbide tools
– Weldable using similar filler metals
– Grinding is the preferred finishing method

## Applications of Stellite12 Alloy

Stellite12 finds use in numerous industrial sectors:

### Oil and Gas Industry

– Valve components
– Pump shafts
– Bearing surfaces
– Downhole tools

### Aerospace Industry

– Turbine blades
– Exhaust components
– Wear pads

### Chemical Processing

– Valve trim

– Pump components
– Nozzles

### Power Generation

– Steam turbine components
– Boiler feed pump parts
– Bushing and bearing applications

## Advantages Over Other Alloys

Stellite12 offers several benefits compared to alternative materials:

– Better wear resistance than many stainless steels
– Superior high-temperature performance compared to nickel alloys
– More cost-effective than some other cobalt alloys
– Excellent combination of hardness and toughness

## Limitations

Some considerations when using Stellite12:

– Higher cost than standard steels
– Limited availability in some forms
– Challenging to machine in hardened condition
– Heavy weight compared to some alternatives

## Conclusion

Stellite12 (UNS R30012) is a versatile cobalt-based alloy that provides an exceptional balance of wear resistance, corrosion resistance, and high-temperature strength. Its unique combination of properties makes it indispensable for