Cobalt (Stellite)
FERVEO COB 21
covered electrode · stick electrodeCatalogue only
AWS class
E 20-UM-300-CKTL
EN ISO class
E Co 1
Hardness
30–32 HRC
Classification
| AWS class | E 20-UM-300-CKTL |
|---|---|
| EN ISO class | E Co 1 |
| DIN 8555 / EN 14700 | E 20-UM-300-CKTL |
Purpose
- Cobalt-based Co-Cr-Mo hardfacing electrode, low carbon (AWS E20-UM-300-CKTL, EN ISO E Co 1) — the toughest of the FERVEO COB family, moderate hardness (30–32 HRC).
Why it works
Lower carbon content than the rest of the COB family gives finer, more dispersed carbides in the cobalt matrix — trading some hardness for toughness and thermal-shock resistance, which is why it's the reference hardfacing where impact or thermal cycling matters more than pure abrasion.
Fields of application
- Valve seats and seating surfaces, hot extrusion dies, hot-shear blades — parts with impact or repeated thermal cycling combined with wear.
Chemical composition
| Element | Typical, % |
|---|---|
| C | 0.3 |
| Co | balance |
| Cr | 26 |
| Mo | 5.6 |
| Ni | 3 |
Mechanical properties
| Hardness | 30–32 HRC |
|---|
Process
| Polarity | DC+/AC |
|---|
Sizes and part numbers
| Ø | Length | Current | Packaging | Request |
|---|---|---|---|---|
| 3.2 mm | 350 mm | 90–120 A | 5 kg |
Advantages
- The toughest and most thermal-shock resistant of the FERVEO COB family — lower cracking risk than the harder variants (COB 6/COB 12/COB 1).
- Good corrosion and high-temperature oxidation resistance, typical of cobalt-based hardfacing.
- Retains hardness at elevated temperature better than a conventional steel hardfacing deposit.
Limitations
- Hardness (30–32 HRC) clearly lower than COB 6/COB 12/COB 1 — not the choice for pure abrasive wear, where those variants perform better.
- As with any cobalt-based hardfacing, the first pass dilutes with the base metal — full hardness and resistance are only reached from the second layer on.