Stellite 4
About Stellite 4
Name and Equivalent Name: Stellite 4, called Cobalt-Chromium Alloy 4, is a high-performance superalloy with the UNS designation R30004. It conforms to ASTM B426, B659, and AMS 5785 standards. While it has no direct equivalent in DIN, BS, or GB/T standards, it is widely recognized for its high corrosion resistance and thermal stability.
Stellite 4 Basic Introduction
Stellite 4 is a cobalt-based superalloy designed for high-performance applications in harsh environments. Its excellent corrosion resistance and high wear resistance make it ideal for components exposed to friction and chemical attack.
This alloy maintains its strength and hardness at elevated temperatures, performing effectively up to 850°C. Stellite 4 is used in various industries, including power generation, aerospace, oil and gas, and marine, where components face extreme conditions. It finds application in valve seats, turbine blades, and hard-facing solutions to extend service life.
Alternative Superalloys of Stellite 4
Stellite 6 and 12 are common alternatives to Stellite 4, offering slightly different balances of hardness and machinability. Stellite 6 provides better machinability, while Stellite 12 offers higher hardness, making it suitable for applications with more severe wear requirements.
Hastelloy C276 or Inconel 625 can serve as alternatives for applications demanding high corrosion resistance and lower brittleness. Nimonic 90 or Rene 41 may be used where high-temperature strength is critical, especially in the aerospace and energy sectors.
Stellite 4 Design Intention
Stellite 4 was developed to combine wear and corrosion resistance in high-stress environments. It is intended for applications requiring extended service life under mechanical stress and thermal cycling, such as valve seats, turbine blades, and heat exchangers.
The design of Stellite 4 focuses on ensuring long-term performance under challenging conditions. Its cobalt-based matrix ensures hardness and wear resistance, while chromium protects against oxidation and corrosion. Tungsten enhances the alloy’s hardness, making it suitable for components exposed to friction and wear at elevated temperatures.
Stellite 4 Chemical Composition
Stellite 4 features a cobalt matrix with significant chromium and tungsten content. Chromium (29-32%) provides corrosion resistance, while tungsten (12-15%) enhances hardness. The carbon content (2.5-3.0%) improves strength but limits ductility.
Element | Composition (%) |
|---|---|
Cobalt (Co) | Balance |
Chromium (Cr) | 29.0-32.0 |
Tungsten (W) | 12.0-15.0 |
Carbon (C) | 2.5-3.0 |
Nickel (Ni) | Max 3.0 |
Silicon (Si) | Max 1.0 |
Iron (Fe) | Max 3.0 |
Stellite 4 Physical Properties
Stellite 4 offers high density, good thermal conductivity, and excellent stability at elevated temperatures. It provides enhanced corrosion resistance and wear protection.
Property | Value |
|---|---|
Density (g/cm³) | 8.98 |
Melting Point (°C) | 1345 |
Thermal Conductivity (W/(m·K)) | 13.1 |
Elastic Modulus (GPa) | 208 |
Metallographic Structure of Stellite 4 Superalloy
Stellite 4 exhibits a cobalt-based matrix with dispersed carbide phases, primarily tungsten and chromium carbides. This microstructure ensures high wear resistance, making it effective in sliding wear and abrasion applications.
The alloy’s metallographic structure helps maintain mechanical stability under thermal stress. Chromium carbides improve the alloy’s resistance to oxidation, while tungsten enhances hardness. Due to its high carbon content, Stellite 4 may be prone to brittleness, but this is balanced by its exceptional wear and corrosion resistance, making it suitable for high-stress environments.
Stellite 4 Mechanical Properties
Stellite 4 offers excellent tensile strength, yield strength, and high fatigue and thermal stress resistance. It performs well at temperatures up to 850°C, making it suitable for demanding applications.
Property | Value |
|---|---|
Tensile Strength (MPa) | ~950 |
Yield Strength (MPa) | ~550 |
Creep Strength | Effective up to 850°C |
Hardness (HRC) | 50-55 |
Elongation (%) | 5-8% |
Modulus of Elasticity (GPa) | 210 |
Key Features of Stellite 4 Superalloy
Superior Corrosion Resistance Stellite 4 offers excellent resistance to oxidation and corrosion, making it suitable for marine, chemical processing, and oil & gas applications. Chromium in the alloy provides a protective oxide layer that prevents degradation in harsh environments.
High-Temperature Stability The alloy maintains strength and hardness at temperatures up to 850°C, making it effective in heat exchangers, turbines, and other high-temperature equipment.
Exceptional Wear Resistance With dispersed carbides in its microstructure, Stellite 4 provides excellent wear resistance, ensuring durability in components exposed to continuous friction, such as valve seats and sliding tools.
Resistance to Thermal Fatigue Stellite 4 performs well under repeated thermal cycling, retaining its mechanical properties over time. This makes it ideal for applications involving rapid temperature fluctuations, such as power generation turbines.
Limited Machinability but Good Weldability While Stellite 4 is challenging to machine due to its hardness, it offers good weldability for hard-facing applications, extending the lifespan of components like tools and valves.
Stellite 4 Superalloy’s Machinability and Processing
Vacuum Investment Casting: Stellite 4 is suitable for vacuum investment casting due to its high-temperature resistance and precise ability to produce complex shapes. This method ensures minimal oxidation and porosity, ideal for aerospace and high-performance components.
Single Crystal Casting: Stellite 4 is not used for single crystal casting because it contains carbide-forming elements that disrupt the uniform grain structure required for single crystal components.
Equiaxed Crystal Casting: Stellite 4 is well-suited for equiaxed crystal casting. It offers uniform mechanical properties and excellent wear resistance throughout the structure, making it ideal for valve seats and wear-resistant coatings.
Superalloy Directional Casting: Stellite 4 is not optimal for directional casting due to its carbide microstructure, as it does not achieve the grain alignment needed for high-stress turbine components.
Powder Metallurgy Turbine Disc: Stellite 4 is rarely used in powder metallurgy for turbine discs due to its high hardness and limited ductility, making it unsuitable for rotating parts under high mechanical stress.
Superalloy Precision Forging: Stellite 4’s brittleness limits its suitability for precision forging, where materials must undergo significant deformation. However, it is often used in overlays and hard-facing applications.
Superalloy 3D Printing: Due to its hardness and the challenges of controlling solidification, Stellite 4 is not commonly used in 3D printing. Its brittleness presents challenges in additive manufacturing processes.
CNC Machining: Stellite 4 can be machined, but its high hardness makes CNC machining challenging. Specialized cutting tools and grinding processes are typically required to achieve precision.
Superalloy Welding: Stellite 4 is highly suitable for welding, especially for hard-facing applications. It provides excellent wear and corrosion resistance when used as an overlay on components subjected to extreme conditions.
Hot Isostatic Pressing (HIP): HIP improves Stellite 4’s density by eliminating porosity, enhancing its mechanical properties, and extending the fatigue life of components used in demanding applications.
Stellite 4 Superalloy Applications
Aerospace and Aviation: Stellite 4 is used in aircraft engine components, such as valve seats and turbine blades, due to its excellent wear and corrosion resistance under high temperatures.
Power Generation: Stellite 4 is applied to steam turbine components and valves in power plants, providing durability and resistance to erosion under high-pressure steam.
Oil and Gas: Stellite 4 is used in drilling tools and valves, offering high wear resistance and corrosion protection in abrasive and corrosive environments.
Energy: The alloy finds applications in thermal energy systems for components like heat exchangers and gas turbines, ensuring performance under thermal stress.
Marine: Stellite 4 is employed in marine applications such as propeller shafts and pump components, resisting saltwater corrosion and mechanical wear.
Mining: In the mining industry, Stellite 4 is used in crushers, drill bits, and slurry pumps, offering durability in abrasive conditions.
Automotive: The alloy is applied to exhaust valves and other high-performance automotive engine components, providing resistance to wear and thermal fatigue.
Chemical Processing: Stellite 4 is used in chemical reactors and pumps where corrosion resistance is essential for handling aggressive chemicals.
Pharmaceutical and Food: The alloy is used in food and pharmaceutical processing equipment, ensuring non-contaminating surfaces and extended wear life.
Military and Defense: Stellite 4 is utilized in defense components, such as missile parts and armor-piercing rounds, for its wear resistance and strength.
Nuclear: In nuclear reactors, Stellite 4 is used for valve seats and seals, ensuring long-term stability under radiation and thermal cycling.
When to Choose Stellite 4 Superalloy
Custom superalloy parts like Stellite 4 are ideal when components must endure extreme wear, corrosion, and high temperatures. It is especially suitable for high-stress environments, such as aerospace engines, power generation turbines, and oil refinery equipment.
Stellite 4 performs exceptionally well in applications involving thermal cycling and mechanical friction, ensuring durability and reliability under harsh conditions. While challenging to machine, it is excellent for hard-facing and overlay applications. Additionally, it offers long-term resistance to wear and corrosion, making it a top choice for marine, chemical processing, and mining industries.
Explore Related Blogs
