Stellite 3

About Stellite 3

Name and Equivalent Name: Stellite 3 is a cobalt-chromium superalloy with the UNS designation R30003. It conforms to ASTM B426 and B659 standards and the AMS 5793 specification. While there are no direct equivalents in DIN, BS, or GB/T standards, it is classified as a cobalt-chromium alloy designed for high-wear applications.

Stellite 3 Basic Introduction

Stellite 3 is a high-performance cobalt-based alloy known for its excellent abrasion resistance, especially in environments subjected to sliding wear and friction. Its high chromium content ensures superior oxidation and corrosion resistance, while tungsten enhances hardness.

This alloy retains mechanical properties at elevated temperatures, performing well up to 1000°C. It is typically used in aerospace, energy, oil & gas, and mining, where components must endure severe abrasion and extreme thermal cycles. Stellite 3 is also applied in cutting tools, valve seats, and wear-resistant coatings.

Alternative Superalloys of Stellite 3

Alternative materials to Stellite 3 include Stellite 6 and 12, which offer similar wear resistance but better machinability. Inconel 625 and Hastelloy C276 can be considered for high-temperature environments requiring lower brittleness.

Rene 41 or Nimonic 90 are preferred alternatives in applications requiring extreme thermal stability. When corrosion resistance in aggressive chemical environments is essential, Hastelloy alloys may outperform Stellite 3.

Stellite 3 Design Intention

Stellite 3 is designed for severe abrasion and sliding wear applications, focusing on retaining hardness and strength at high temperatures. The alloy is particularly effective in environments where components experience frequent thermal cycling, such as turbine seals, cutting tools, and valve seats.

The design goal of Stellite 3 emphasizes balancing hardness, wear resistance, and toughness. It provides superior performance in abrasive environments and is ideal for applications involving mechanical stress and high heat exposure, such as industrial turbines and mining equipment.

Stellite 3 Chemical Composition

Stellite 3 achieves its abrasion resistance and strength through a cobalt matrix reinforced by chromium and tungsten. Chromium (31-33%) offers corrosion resistance, while tungsten (14-16%) ensures hardness. Carbon (3.0-3.6%) enhances the alloy’s strength, although higher carbon content makes it more brittle.

Stellite 3 Physical Properties

Stellite 3 is characterized by its high density and thermal stability, which allows it to perform effectively in high-stress environments. Its superior thermal conductivity ensures heat dissipation, reducing thermal fatigue.

Metallographic Structure of Stellite 3 Superalloy

Stellite 3 features a dense cobalt matrix with fine carbide precipitates throughout the microstructure. The primary carbides are chromium-based, which provide excellent wear resistance under high-stress conditions. Tungsten enhances the formation of hard phases, making the alloy highly abrasion-resistant.

Due to its high carbon content, Stellite 3 has limited ductility, leading to brittleness, especially at lower temperatures. However, the alloy's structure ensures superior performance in environments with high thermal cycling, where hardness and mechanical stability are essential.

Stellite 3 Mechanical Properties

Stellite 3 offers high tensile and yield strength and excellent abrasion and thermal fatigue resistance. It maintains strength and stability at elevated temperatures, with strong performance even at 850°C.

Key Features of Stellite 3 Superalloy

1. Exceptional Abrasion Resistance Stellite 3 offers excellent resistance to sliding wear and abrasion, making it ideal for cutting tools and valve seats exposed to continuous mechanical stress. Its hard carbide structure ensures long service life even under severe friction.

2. High-Temperature Stability The alloy retains strength and hardness at temperatures up to 1000°C, making it suitable for use in turbines, heat exchangers, and industrial machinery exposed to thermal cycles.

3. Corrosion and Oxidation Resistance With a high chromium content, Stellite 3 resists corrosion and oxidation in aggressive environments, ensuring durability in chemical processing and marine applications.

4. Resistance to Thermal Cycling Stellite 3 excels in environments with rapid temperature changes, maintaining mechanical stability without significant degradation, which is essential for components like turbine seals and nozzles.

5. Limited Machinability but Excellent Weldability The alloy’s hardness makes it challenging to machine using conventional methods, often requiring precision grinding. However, it can be effectively welded, especially for hard-facing applications, ensuring long-lasting performance.

Stellite 3 Superalloy’s Machinability and Processing

• Vacuum Investment Casting: Stellite 3 can be used in vacuum investment casting to produce complex, high-wear components due to its excellent wear resistance and high-temperature stability. Its hardness requires precise control during casting to avoid cracking.

• Single Crystal Casting: Stellite 3 is unsuitable for single crystal casting as its high carbon content leads to carbide formation, making it incompatible with the single-crystal structure required for creep resistance in aerospace components.

• Equiaxed Crystal Casting: Stellite 3 performs well in equiaxed crystal casting, especially for components where uniform properties are needed throughout the material, such as valve seats and wear-resistant coatings.

• Superalloy Directional Casting: Directional casting is not ideal for Stellite 3 since the alloy's microstructure doesn't align with the directional grain requirements for high-performance turbine blades.

• Powder Metallurgy Turbine Disc: Stellite 3 is not typically used in powder metallurgy for turbine discs due to its limited ductility and brittleness, which restricts performance in rotating components.

• Superalloy Precision Forging: Stellite 3’s brittleness makes it challenging to forge, limiting its use in precision forging, where materials must undergo significant deformation.

• Superalloy 3D Printing: Stellite 3 is rarely used in 3D printing due to challenges with cracking during solidification and its high hardness, which complicates additive manufacturing processes.

• CNC Machining: Stellite 3 can be used in CNC machining, but its extreme hardness requires specialized tooling and techniques, such as grinding, to achieve precision.

• Superalloy Welding: Stellite 3 is suitable for welding, especially in hard-facing applications, offering enhanced wear resistance and extended service life for critical components.

• Hot Isostatic Pressing (HIP): HIP is beneficial for Stellite 3 in improving density and eliminating porosity, resulting in better mechanical properties and extended fatigue life in demanding applications.

Stellite 3 Superalloy Applications

• Aerospace and Aviation: Stellite 3 is used in aerospace components like valve seats, turbine seals, and exhaust nozzles, where wear resistance and thermal stability are critical.

• Power Generation: Stellite 3 is applied to steam turbine blades and control valves in power plants, offering abrasion resistance and durability under high-pressure steam conditions.

• Oil and Gas: Stellite 3 is used in valve seats, drilling tools, and refinery equipment, ensuring resistance to wear, corrosion, and high-pressure environments.

• Energy: Stellite 3 is employed in thermal power generation and energy systems for components subject to wear and thermal cycling, enhancing reliability.

• Marine: The alloy is used in propeller shafts, pump components, and valve seats, where saltwater corrosion resistance and mechanical stability are essential.

• Mining: Stellite 3 finds applications in mining tools like drill bits, crushers, and slurry pumps, offering long-lasting wear resistance in abrasive conditions.

• Automotive: Stellite 3 is applied to exhaust valves in high-performance automotive engines, improving thermal fatigue and mechanical wear resistance.

• Chemical Processing: Stellite 3 is used in chemical reactors, pumps, and valves where corrosion resistance and wear protection are required in harsh environments.

• Pharmaceutical and Food: The alloy is employed in processing equipment requiring non-contaminating properties and wear resistance, ensuring durability in hygienic conditions.

• Military and Defense: Stellite 3 is used in missile components, armor-piercing rounds, and defense equipment, providing wear resistance and strength under extreme conditions.

• Nuclear: Stellite 3 is applied in nuclear reactors for critical components like valve seats and seals that must withstand radiation and thermal cycling.

When to Choose Stellite 3 Superalloy

Custom superalloy parts like Stellite 3 are recommended when exceptional wear resistance, thermal stability, and corrosion resistance are needed. This alloy performs well in high-temperature environments with significant abrasion and thermal cycling, making it ideal for aerospace turbines, oil drilling tools, and chemical reactors. It excels in industries where components are exposed to harsh conditions, ensuring long service life.

However, Stellite 3 is better suited for hard-facing applications or precision machining involving grinding due to its hardness and brittleness. It is also favored for welding overlays, providing extended durability to critical components. Stellite 3’s unique combination of mechanical properties and high-temperature performance makes it an excellent choice for power generation, marine, and mining applications where reliability and resistance to wear are critical.