Stellite 21 vs Stellite 6: 57% composition overlap. Moderate differences, generally not direct substitutes.
Stellite 21 vs Stellite 6
Side-by-side chemical composition and mechanical property comparison.
Overview
Stellite 21
R30021
Low-carbon cobalt-chromium-molybdenum alloy optimized for cavitation, galling, and corrosion resistance rather than abrasive wear. CoCrMo matrix without tungsten — Mo replaces W for superior corrosion resistance in reducing environments. Lower hardness (25-35 HRC) than Stellite 6 but better ductility and thermal/mechanical shock resistance. Used for valve seats in corrosive service, pump components in chemical processing, hot gas path components, and nuclear valve hardfacing. Also used as dental/orthopedic implant hardfacing.
Stellite 6
R30006
The world's most widely used cobalt-based wear-resistant alloy. CoCrW matrix with hard chromium carbides (M7C3) provides exceptional resistance to abrasion, erosion, cavitation, galling, and corrosion across a wide temperature range. Retains hardness up to 500°C. Non-magnetic. Industry standard for general-purpose wear resistance — suitable for hardfacing (PTA, laser, TIG), casting, and powder metallurgy. Used for valve seats, pump sleeves, bearing surfaces, cutting tools, hot-forming dies, and turbine blade erosion shields.
| Stellite 21 | Stellite 6 | |
|---|---|---|
| Material Number | R30021 | R30006 |
| Category | cobalt | cobalt |
| Standard | AMS 5895 | AMS 5894 |
Chemical composition (wt%)
| Element | Stellite 21 | Stellite 6 | Overlap |
|---|---|---|---|
| C | ≤ 0.35% | 0.9–1.4% | No overlap |
| Si | ≤ 1.5% | ≤ 1.5% | OK |
| Mn | ≤ 1% | ≤ 1% | OK |
| Cr | 26–29% | 26–32% | OK |
Mechanical properties
| Property | Stellite 21 | Stellite 6 | Unit |
|---|---|---|---|
| hardness_hrc | 25–35 | 36–45 | HRC |
| density | ≥ 8.33 | ≥ 8.39 | g/cm3 |
| tensile_strength | — | ≥ 896 | MPa |
Compatibility Assessment
Stellite 21 and Stellite 6 have moderate differences (57% overlap). They are generally not direct substitutes. Consider the specific requirements of your application.
Automated assessment based on composition analysis
Frequently Asked Questions
Is Stellite 21 the same as Stellite 6?
Stellite 21 and Stellite 6 have a 57% composition overlap. They are generally not directly interchangeable.
Can I replace Stellite 21 with Stellite 6?
Generally not recommended. The compositions differ significantly (57% overlap). These materials have different alloying concepts and are intended for different applications.
What is the difference between Stellite 21 and Stellite 6?
The main differences are in the following elements: C, Mo. Stellite 21 is a cobalt grade, while Stellite 6 is a cobalt grade.
View full data for each material:
Data provided for reference only. Always verify against the applicable specification for critical applications.
All data is for reference only. Equivalents indicate similarity, not identity. Always verify against the applicable specification for safety-critical applications. materialref.com accepts no liability for decisions based on this data.