Stellite 21

Stellite 21 is a low-carbon cobalt-chromium-molybdenum alloy. Compared with Stellite 6 and Stellite 12, it emphasizes toughness, corrosion resistance, and thermal-shock resistance rather than maximum hardness. It maintains good stability under elevated temperatures, corrosive conditions, and repeated mechanical loading.

Appearance & Properties

Color: Silver-gray to bright silver-gray

Density: Approx. 8.3 g/cm³

Hardness: Typically approx. 27–40 HRC, depending on product form, work hardening, and condition

Corrosion Resistance: Excellent

High-Temperature Performance: Excellent

Wear Resistance: Good

Machinability: Difficult

Toughness: Better than Stellite 6 and Stellite 12

Thermal-Shock Resistance: Good

Magnetism: Generally somewhat magnetic

Surface Finishes: Grinding, polishing, blasting, precision grinding, etc.

Typical Applications

Stellite 21 is widely used in petrochemical, energy, aerospace, pumps and valves, marine, and high-temperature industrial equipment.

Typical parts include high-temperature valve trim, valve seats, valve components, pump parts, sealing rings, bushings, hot-section components, and corrosion- and wear-resistant precision parts.

Advantages

• Excellent corrosion resistance and high-temperature performance

• Better toughness than Stellite 6 and Stellite 12

• Good thermal-shock and fatigue resistance

• Good wear and anti-galling performance

• Suitable for combined heat, corrosion, and impact conditions

Limitations

• Lower hardness and wear resistance than Stellite 6 and Stellite 12

• Difficult to CNC machine

• Work hardening can further increase machining difficulty

• High material and machining costs