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July 19, 2025| | 0 Comment

Stellite 21 Alloy (UNS R30021) Properties and Applications

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Stellite 21 Alloy (UNS R30021) Properties and Applications

Introduction

Stellite 21, also known by its UNS designation R30021, is a cobalt-based superalloy renowned for its exceptional resistance to wear, corrosion, and high-temperature oxidation. This alloy is widely used in demanding industrial applications where durability and performance under extreme conditions are critical.

Chemical Composition

The chemical composition of Stellite 21 includes:

  • Cobalt (Co): Primary base element

  • Chromium (Cr): 26-30%

  • Molybdenum (Mo): 5-7%

  • Nickel (Ni): 2-4%

  • Iron (Fe): ≤3%

  • Carbon (C): 0.25% max

  • Silicon (Si): ≤1%

  • Manganese (Mn): ≤1%

Key Properties

Stellite 21 exhibits several remarkable properties that make it suitable for challenging environments:

  • High Wear Resistance: Excellent performance in abrasive and sliding wear conditions.

  • Corrosion Resistance: Resists oxidation and corrosion in acidic and alkaline environments.

  • High-Temperature Stability: Maintains mechanical properties at elevated temperatures up to 1000°C (1832°F).

  • Good Machinability: Can be machined using conventional methods, though it is harder than many steels.

  • Biocompatibility: Suitable for medical implants due to its non-reactive nature.

Applications

Due to its unique combination of properties, Stellite 21 is used in various industries, including:

  • Aerospace: Components like turbine blades, exhaust valves, and combustion chambers.

  • Oil & Gas: Valves, pump components, and drilling tools exposed to corrosive environments.

  • Medical: Orthopedic implants and surgical instruments.

  • Industrial: Wear-resistant coatings, cutting tools, and dies.

  • Automotive: High-performance engine parts and exhaust systems.

Conclusion

Stellite 21 (UNS R30021) is a versatile superalloy with outstanding wear, corrosion, and high-temperature resistance. Its applications span multiple industries, making it a critical material for demanding engineering challenges. Whether in aerospace, medical, or industrial settings, Stellite 21 continues to prove its value as a reliable and high-performance alloy.