Name and Equivalent Name: Stellite 6B, called Cobalt-Chromium Alloy 6B, carries the UNS designation R30016. It conforms to ASTM F1537, F75, B659, and ISO 5832-4 standards. Equivalent names include GB/T 15025: CoCrW6B, and it also follows AMS 5894 and ASME SB-75 specifications, approved for use under NACE MR0175.
Stellite 6B is a cobalt-based superalloy known for its exceptional wear resistance, corrosion resistance, and high mechanical stability at elevated temperatures. Its primary use lies in applications where components face continuous mechanical friction and chemical exposure, such as valves, pumps, and turbine blades.
This alloy retains its mechanical properties at temperatures up to 850°C, offering high creep resistance for over 10,000 hours. Stellite 6B is frequently used in aerospace, energy, chemical processing, and oil & gas industries, where durability under extreme conditions is essential.
Alternatives to Stellite 6B include Stellite 6 and Stellite 21. Stellite 6 provides slightly better machinability, while Stellite 21 offers superior corrosion resistance but with lower hardness.
In applications requiring higher oxidation resistance or mechanical strength, Inconel 718 or Hastelloy C22 may be suitable alternatives. Rene 41 and Nimonic 90 are viable options for applications with significant thermal cycling due to their superior creep resistance at high temperatures.
Stellite 6B balances wear resistance, corrosion protection, and high creep strength. It is intended for sliding wear environments, high temperatures, and chemical exposure.
The alloy’s primary applications include valve seats, pump components, and heat exchangers. Its formulation focuses on ensuring long service life in demanding conditions, particularly in the aerospace, energy, and chemical industries, where mechanical performance and durability are crucial.
Stellite 6B consists primarily of cobalt, with significant amounts of chromium to enhance corrosion resistance and tungsten to increase hardness. Carbon provides strength, though it may reduce ductility.
Element | Composition (%) |
---|---|
Cobalt (Co) | Balance |
Chromium (Cr) | 27.0-32.0 |
Tungsten (W) | 4.0-6.0 |
Carbon (C) | 0.95-1.2 |
Nickel (Ni) | Max 3.0 |
Silicon (Si) | Max 1.0 |
Iron (Fe) | Max 3.0 |
Stellite 6B is characterized by high density, good thermal conductivity, and excellent thermal fatigue resistance. It remains stable under high temperatures and stress, withstanding prolonged exposure without degradation.
Property | Value |
---|---|
Density (g/cm³) | 8.8 |
Melting Point (°C) | 1335 |
Thermal Conductivity (W/(m·K)) | 12.6 |
Elastic Modulus (GPa) | 205 |
Stellite 6B exhibits a cobalt-based matrix with finely dispersed carbides, primarily chromium and tungsten carbides. This microstructure ensures excellent wear resistance and mechanical stability under sliding and abrasive conditions.
The alloy’s carbides improve its resistance to oxidation and corrosion, while the cobalt matrix provides toughness. Although the high carbon content enhances strength, it also reduces ductility, requiring careful machining and welding processes. Stellite 6B is suitable for components that must maintain performance under continuous mechanical stress and thermal cycling.
Stellite 6B offers high tensile and yield strength with superior creep resistance at elevated temperatures. It remains stable during long-term exposure to high-temperature environments.
Property | Value |
---|---|
Tensile Strength (MPa) | ~900 |
Yield Strength (MPa) | 450-600 |
Creep Resistance | High at 850°C |
Hardness (HRC) | 45-50 |
Elongation (%) | 5-10% |
Modulus of Elasticity (GPa) | 205 |
Exceptional Wear Resistance Stellite 6B offers outstanding resistance to sliding wear and abrasion, making it ideal for valve seats, cutting tools, and pump components subjected to friction and mechanical stress.
Thermal Stability and Creep Resistance The alloy retains strength and creep resistance at temperatures up to 850°C, ensuring long-term stability even after 10,000 hours of exposure in high-temperature environments.
Excellent Corrosion Resistance With a high chromium content, Stellite 6B forms a protective oxide layer, providing superior corrosion resistance in chemical, marine, and oil & gas applications.
Thermal Fatigue Resistance Stellite 6B performs well under thermal cycling, maintaining mechanical integrity in turbines, heat exchangers, and energy systems exposed to fluctuating temperatures.
Weldability and Hard-Facing Capability While Stellite 6B’s hardness makes machining challenging, it offers excellent weldability. It is widely used for hard-facing applications, extending the service life of critical components in demanding industries.
Vacuum Investment Casting: Stellite 6B is well-suited for vacuum investment casting due to its corrosion resistance and ability to retain hardness at high temperatures. This process ensures precise, oxidation-free components suitable for aerospace and industrial applications.
Single Crystal Casting: Stellite 6B is unsuitable for single crystal casting. Its microstructure relies on dispersed carbides, which disrupt the continuous grain structure required for single-crystal applications in turbine blades.
Equiaxed Crystal Casting: Equiaxed crystal casting is an effective method for processing Stellite 6B, providing uniform properties across the entire component. This makes it ideal for valves and pump components where wear resistance is critical.
Superalloy Directional Casting: Due to its carbides and inherent microstructure, Stellite 6B is not optimal for directional casting, which requires aligned grain structures for enhanced mechanical performance in turbine components.
Powder Metallurgy Turbine Disc: Stellite 6B is rarely used in powder metallurgy for turbine discs due to its limited ductility and tendency to crack under stress, making it unsuitable for high-speed rotating parts.
Superalloy Precision Forging: Stellite 6B’s brittleness limits its applicability in precision forging, though it can be used for overlay applications where wear resistance is critical.
Superalloy 3D Printing: Stellite 6B presents challenges in 3D printing due to carbide formation, which can lead to cracking. Specialized post-processing treatments are required to ensure the desired mechanical properties.
CNC Machining: Stellite 6B is difficult to machine due to its hardness and abrasion resistance. CNC machining with specialized tools is essential, often involving grinding to achieve precise dimensions.
Superalloy Welding: Stellite 6B is highly suitable for welding, particularly for hard-facing applications, where it provides excellent protection against wear and corrosion, extending component lifespan.
Hot Isostatic Pressing (HIP): HIP enhances the mechanical properties of Stellite 6B by eliminating internal porosity, improving fatigue resistance, and ensuring long-term reliability under thermal cycling.
Aerospace and Aviation: Stellite 6B is used in aerospace engines for valve seats, bearings, and turbine blades, providing exceptional wear resistance and thermal stability under high temperatures.
Power Generation: In power plants, Stellite 6B is applied to turbine components, steam valves, and heat exchangers, ensuring durability under high-pressure conditions and thermal cycling.
Oil and Gas: The alloy is used for drill bits, valve seats, and refinery equipment, providing superior wear resistance and corrosion protection in abrasive, high-pressure environments.
Energy: Stellite 6B performs well in gas turbines and energy systems, ensuring reliability under high temperatures and resistance to mechanical wear and corrosion.
Marine: In marine applications, Stellite 6B is used for propeller shafts, pumps, and valves, providing excellent resistance to saltwater corrosion and mechanical abrasion.
Mining: Stellite 6B is applied to crushers, slurry pumps, and drill bits, offering outstanding wear resistance and reliability in abrasive mining environments.
Automotive: The alloy is used in exhaust valves and other engine components that demand high wear resistance and thermal stability under extreme conditions.
Chemical Processing: Stellite 6B is ideal for chemical reactors, pumps, and valves, providing excellent corrosion resistance in aggressive chemical environments.
Pharmaceutical and Food: The alloy ensures non-contaminating surfaces in food and pharmaceutical equipment, offering wear resistance and long-term reliability.
Military and Defense: Stellite 6B is employed in missile components and armor-piercing rounds, providing high wear resistance and performance in extreme conditions.
Nuclear: In nuclear reactors, Stellite 6B is used for valve seats and seals, offering long-term stability under high radiation exposure and thermal stress.
Choosing custom superalloy parts like Stellite 6B is essential when components must withstand high wear, corrosion, and thermal stress. It is the ideal choice for aerospace, power generation, and oil & gas industries, where materials are exposed to friction, chemicals, and extreme temperatures.
Stellite 6B performs exceptionally well in applications requiring long-term reliability, such as valves, turbine blades, and heat exchangers. Although machining can be challenging, its superior weldability makes it an excellent option for hard-facing applications, ensuring extended component life. For demanding environments, Stellite 6B offers a balance of durability, corrosion resistance, and thermal stability.