Stellite 12
About Stellite 12
Name and Equivalent Name: Stellite 12, also called Cobalt-Chromium Alloy 12, has the UNS designation R30012. It complies with ASTM B426, B659, and ISO 5832-4 standards. Equivalent names include DIN/EN 2.4725 and GB/T 15025: CoCrW12, with additional classification under AMS 5391 and approved usage under NACE MR0175.
Stellite 12 Basic Introduction
Stellite 12 is a high-performance alloy primarily composed of cobalt and chromium, designed for superior wear resistance and durability in high-temperature applications. The alloy is enriched with tungsten and carbon, which provide additional hardness, making it ideal for environments where components are subjected to abrasive wear and chemical exposure.
With excellent mechanical stability at elevated temperatures, Stellite 12 finds applications in aerospace, oil & gas, and energy industries. This alloy is commonly used for valve seats, cutting tools, and turbine components, where its strength and corrosion resistance ensure long service life with minimal maintenance.
Alternative Superalloys of Stellite 12
Stellite 12 balances hardness and corrosion resistance, but other alloys like Stellite 6 provide improved ductility, making them more suitable for applications requiring greater flexibility. Stellite 21 is a better option where superior corrosion resistance is required, though it sacrifices some hardness.
Due to their enhanced oxidation resistance, Inconel 718 or Hastelloy C22 may be considered alternatives for high-temperature aerospace applications. Nimonic 90 and Rene 41 are other viable options for demanding high-temperature conditions where thermal fatigue resistance is essential.
Stellite 12 Design Intention
The design of Stellite 12 focuses on delivering wear resistance, corrosion protection, and mechanical stability under high temperatures. This makes it ideal for components exposed to mechanical friction and chemical attack, such as pump seals, cutting tools, and valve seats.
Stellite 12 is engineered for applications requiring minimal maintenance and long-term performance, particularly in harsh environments. Its hardness and corrosion resistance combination ensures durability in turbines, energy systems, and chemical reactors, reducing downtime and extending service life.
Stellite 12 Chemical Composition
Stellite 12’s composition leverages chromium for corrosion resistance and tungsten for enhanced hardness. Carbon contributes to strength but limits ductility, making it suitable for wear-intensive applications.
Element | Composition (%) |
|---|---|
Cobalt (Co) | Balance |
Chromium (Cr) | 27.0-32.0 |
Tungsten (W) | 8.0-10.5 |
Carbon (C) | 1.0-1.4 |
Nickel (Ni) | Max 3.0 |
Silicon (Si) | Max 1.0 |
Iron (Fe) | Max 3.0 |
Stellite 12 Physical Properties
Stellite 12 maintains strength and stability at high temperatures, with excellent thermal conductivity and good wear resistance, even in extreme conditions.
Property | Value |
|---|---|
Density (g/cm³) | 8.83 |
Melting Point (°C) | 1335 |
Thermal Conductivity (W/(m·K)) | 13.2 |
Elastic Modulus (GPa) | 207 |
Metallographic Structure of Stellite 12 Superalloy
The microstructure of Stellite 12 consists of a cobalt-based matrix with dispersed tungsten and chromium carbides. These carbides provide exceptional wear resistance, ensuring durability in components subject to abrasive conditions.
The chromium content allows the alloy to form a protective oxide layer, enhancing corrosion resistance. However, the high carbon content makes the material relatively brittle, which limits its use in applications that require high ductility. Despite this, Stellite 12 remains highly effective in high-temperature and chemically aggressive environments.
Stellite 12 Mechanical Properties
Stellite 12 offers high tensile strength, excellent hardness, and good elongation, ensuring mechanical stability in high-stress environments and long service life at elevated temperatures.
Property | Value |
|---|---|
Tensile Strength (MPa) | 900-950 |
Yield Strength (MPa) | ~600 |
Creep Strength | Excellent at high temperatures |
Hardness (HRC) | 45-50 |
Elongation (%) | 2-5% |
Modulus of Elasticity (GPa) | 210 |
Key Features of Stellite 12 Superalloy
Exceptional Wear Resistance Stellite 12 provides superior sliding and abrasive wear resistance, making it ideal for valve seats, cutting tools, and pump components subjected to high mechanical stress.
Thermal Stability and Creep Resistance The alloy retains strength and stability at elevated temperatures, offering excellent creep resistance in turbines and other high-temperature systems.
Corrosion Resistance With a high chromium content, Stellite 12 forms a protective oxide layer that ensures corrosion resistance in chemically aggressive environments, including chemical processing and marine applications.
Hardness for Extreme Applications Stellite 12’s tungsten content enhances hardness, making it suitable for applications that require durable cutting tools and wear-resistant coatings.
Long-Term Reliability Designed for harsh environments, Stellite 12 delivers long-term performance with minimal maintenance, ensuring operational efficiency and reducing downtime in critical industries.
Stellite 12 Superalloy’s Machinability and Processing
Vacuum Investment Casting: Stellite 12 is compatible with vacuum investment casting, ensuring minimal oxidation. This method is ideal for creating high-quality, precision components used in aerospace and power industries.
Single Crystal Casting: Stellite 12 is unsuitable for single crystal casting due to its carbide microstructure, which disrupts the continuous grain growth required for this process, commonly used in advanced turbine blades.
Equiaxed Crystal Casting: Stellite 12 performs well in equiaxed crystal casting, providing uniform mechanical properties and making it a preferred option for valve seats and wear-resistant pump components.
Superalloy Directional Casting: Due to its high carbide content, Stellite 12 is unsuitable for directional casting, which relies on aligned grains to enhance mechanical properties for rotating components.
Powder Metallurgy Turbine Disc: Stellite 12 is generally not used for powder metallurgy turbine discs, as it lacks the required ductility for high-speed rotating parts subjected to mechanical stress.
Superalloy Precision Forging: Stellite 12 is not ideal for traditional precision forging but performs well in overlay applications to enhance wear resistance in critical components due to its hardness.
Superalloy 3D Printing: Stellite 12 poses challenges for 3D printing due to carbide formation, which can result in cracking. However, advanced post-processing can improve mechanical performance.
CNC Machining: Stellite 12 is suitable for CNC machining, though its hardness demands specialized tools and grinding techniques to achieve precision in components like valves and cutting tools.
Superalloy Welding: Stellite 12 offers excellent weldability, making it ideal for hard-facing applications where wear resistance and corrosion protection are essential.
Hot Isostatic Pressing (HIP): HIP benefits Stellite 12 by eliminating porosity and enhancing mechanical properties, ensuring long-term thermal and mechanical stress performance.
Stellite 12 Superalloy Applications
Aerospace and Aviation: Stellite 12 is used in aerospace engines for valve seats and turbine blades, where its wear resistance ensures reliability in high-temperature environments.
Power Generation: Stellite 12 is used in steam turbines and heat exchangers in power plants, providing superior performance under extreme conditions and thermal cycling.
Oil and Gas: The alloy is ideal for valves, drill bits, and refinery equipment, offering exceptional corrosion resistance in high-pressure and abrasive environments.
Energy: Stellite 12 performs well in gas turbines and energy systems, providing durability under high thermal and mechanical stress.
Marine: In marine environments, Stellite 12 is used for pumps, valves, and propeller shafts, offering resistance to saltwater corrosion and abrasive wear.
Mining: Stellite 12 is applied to crushers and slurry pumps, providing wear resistance in highly abrasive conditions and extending component lifespan.
Automotive: The alloy is used in exhaust valves and engine components, ensuring high-temperature wear and thermal fatigue resistance.
Chemical Processing: Stellite 12 is ideal for pumps and valves in chemical reactors, offering corrosion resistance in aggressive chemical environments.
Pharmaceutical and Food: Stellite 12 ensures non-contaminating surfaces in pharmaceutical and food processing equipment, providing long-term reliability.
Military and Defense: The alloy is used in defense components, such as missile parts and protective coatings, offering wear resistance under extreme conditions.
Nuclear: Stellite 12 is employed in nuclear reactors for valve seats and seals, ensuring stability under high radiation and thermal stress.
When to Choose Stellite 12 Superalloy
Custom superalloy parts like Stellite 12 are essential when components face extreme wear, high temperatures, and chemical exposure. The alloy is ideal for industries that require durable materials with minimal maintenance, such as aerospace, power generation, and oil & gas.
Stellite 12 excels in applications with critical mechanical strength and corrosion resistance, such as valves, turbine blades, and heat exchangers. Although it presents challenges for machining, its superior weldability makes it highly effective for hard-facing applications. For high-performance components, Stellite 12 ensures reliable and long-lasting service.
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