Stellite 21 Cobalt-Based Alloy

Stellite 21 is a high-performance cobalt-chromium-molybdenum (CoCrMo) alloy renowned for its exceptional wear resistance, corrosion resistance, and ability to maintain mechanical properties at elevated temperatures. Originally developed as Stellite 8, it gained prominence in biomedical applications, including hip implants and dentures, before being adapted for industrial uses such as aerospace, power generation, and tooling.

Nominal Composition (Mass %)

Physical Properties

Composition and Microstructure

Stellite 21 consists of a CoCrMo matrix reinforced with finely dispersed hard carbides, which enhance strength and wear resistance while reducing ductility. The alloy’s microstructure—particularly the carbide size, shape, and distribution—is highly dependent on manufacturing methods (casting, powder metallurgy, or welding) and subsequent heat treatments.

Key Properties

1. Wear Resistance

   • Excellent resistance to cavitation, galling, and metal-to-metal sliding wear.

   • Not ideal for severe abrasive wear due to its relatively low carbide volume fraction.

   • Exhibits work hardening during machining or wear, necessitating specialized tooling for fabrication.

2. Corrosion & Heat Resistance

   • Maintains performance in aggressive chemical environments and high temperatures.

   • Used in petrochemical valve trim, power plant components, and hot forging dies.

3. Thermal and Mechanical Shock Resistance

   • Withstands rapid temperature fluctuations, making it suitable for aerospace and high-stress tooling applications.

4. Biocompatibility

   • Early medical applications leveraged its corrosion resistance and biocompatibility for implants and dental prosthetics.

Processing and Heat Treatment

• Solution treatment (1200–1240°C / 2190–2265°F) followed by quenching and aging (700–1150°C / 1290–2100°F) optimizes high-temperature strength.

• Can be cast, sintered via powder metallurgy, or applied as a weld overlay (excluding oxyacetylene deposition).

Applications

• Industrial: Valve components, pump parts, extrusion dies, and hot forging tools.

• Aerospace: Early jet engine trials due to heat resistance.

• Medical: Historical use in implants; modern variants still in biomedical applications.

Stellite 21 remains a versatile, high-performance alloy for extreme environments where wear, corrosion, and thermal stability are critical. Its adaptability across industries—from medical to aerospace—highlights its enduring engineering value.

Lork Group is a leading supplier of high-temperature superalloys, cobalt-based alloys (like Stellite 21), and specialty metals for extreme environments. We provide premium materials for aerospace, power generation, petrochemical, and medical industries—ensuring superior wear resistance, corrosion resistance, and thermal stability.

🔹 Products: Nickel-based superalloys, cobalt alloys (Stellite series), heat-resistant steels
🔹 Applications: Turbine blades, valves, forging dies, biomedical implants
🔹 Services: Custom alloys, precision machining, technical support

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