Overview
Stellite 6 and Stellite 21 are both very commonly used Stellite alloys. However, if you are not very familiar with these two materials, you may find it difficult to recognize the differences between them. This can affect your material selection decision. Therefore, this article will compare Stellite 6 and Stellite 21 alloys from various aspects. We believe it will play a crucial role in your decision-making.
Basic Information
Name
Stellite 6
UNS R30006
Brand
SATELLITE®
Matrix
Density
8.44 g/cm³
Use Temperature
High Temperature
Name
Stellite 21
UNS R30021
Brand
SATELLITE®
Matrix
Density
8.33 g/cm³
Use Temperature
High Temperature
Introduction
Stellite 6
Stellite 6 is the most widely used of the wear resistant cobalt-based alloys and exhibits good all-round performance. It is regarded as the industry standard for general-purpose wear resistance applications, has excellent resistance to many forms of mechanical and chemical degradation over a wide temperature range, and retains a reasonable level of hardness up to 500°C (930°F). It also has good resistance to impact and cavitation erosion.
Stellite 21
Stellite 21 consists of a CoCrMo alloy matrix containing dispersed hard carbides which strengthen the alloy and increase its hardness, but also decrease the ductility.
The type, shape, size, and distribution of the carbides is strongly influenced by the processing history of the alloy, and for this reason the mechanical properties of Stellite 21 are very dependent upon the manufacturing route and any subsequent heat treatments.
Chemical Composition
Corrosion Resistance
Stellite 6
lose
Stellite 21
WIN
Both Stellite 6 and Stellite 21 exhibit excellent corrosion resistance. However, Stellite 21 offers superior overall corrosion resistance.
Corrosion is generally classified into oxidizing corrosion and reducing corrosion. Chromium is the element that determines resistance to oxidizing corrosion. Stellite 6 has a higher chromium content, resulting in better oxidation resistance.
For reducing corrosion, molybdenum is crucial. Stellite 21 contains 5%–6% molybdenum, giving it resistance to reducing corrosion that Stellite 6 lacks. Therefore, if you require materials to operate in complex environments, Stellite 21 is a better choice.
High Temperature Resistance
Stellite 6
Tie
Stellite 21
Tie
As Stellite alloys, both Stellite 6 and Stellite 21 exhibit excellent high-temperature resistance. Cobalt is a crucial element for high-temperature resistance, and Stellite 21 has a higher cobalt content, thus its high-temperature resistance is slightly better.
Wear Resistance
Stellite 6
WIN
Stellite 21
lose
As wear-resistant alloys, both Stellite 6 and Stellite 21 offer good wear resistance. However, Stellite 6 undoubtedly boasts superior wear resistance.
Firstly, Stellite 6 has a significantly higher carbon content than Stellite 21, and carbon content is a key factor in the wear resistance of Stellite alloys.
Secondly, tungsten is also a crucial element determining the wear resistance of an alloy. Stellite 6 contains up to 5.5% tungsten, while Stellite 21 contains none. This further widens the gap in their wear resistance.
Therefore, if your application requires a material with higher wear resistance, Stellite 6 is the better choice.
Main Standards
Stellite 6
Filler Metal: AWS A5.21 ERCoCr-A
Welding Electrode: AWS A5.13 ECoCr-A
Stellite 21
Filler Metal: AWS A5.21 ERCoCr-E
Welding Electrode: AWS A5.13 ECoCr-E
Price
Stellite 6
Tie
Stellite 21
Tie
There is no significant price difference between Stellite 6 and Stellite 21. The main factors affecting the price are cobalt, molybdenum, and tungsten. Stellite 21 has a slightly higher cobalt content than Stellite 6. Meanwhile, the molybdenum content of Stellite 21 is also slightly higher than the tungsten content of Stellite 6. Therefore, Stellite 21 is slightly more expensive.
Conclusion
Both Stellite 6 and Stellite 21 are wear-resistant and corrosion-resistant alloys. However, Stellite 6 prioritizes wear resistance, while Stellite 21 prioritizes corrosion resistance. Therefore, you can choose the appropriate material based on your specific application.
We manufacture various Stellite 6 and Stellite 21 products strictly according to standards. If you have any corresponding needs, please do not hesitate to contact us.
