Cobalt-Chrome Alloy Stellite 21 As Welded
Finish state
UNS R30021 · also CoCrMo Stellite
Use for cladding valve seats, dies and shafts; hardness rises substantially by work hardening in service.
Values for the As Welded condition
Other Stellite 21 tempers and conditions
Stellite 21 is listed in 5 conditions; see the grade overview at Stellite 21.
- As Welded
- As Cast
- HIP
- Aged
- Hot Worked
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
As WeldedThis page hardfacing overlay (PTA/GTAW/SMAW), undiluted deposit | Use for cladding valve seats, dies and shafts; hardness rises substantially by work hardening in service. | 490 | 700 | 8 | 32 HRC | 2 % IACS |
As CastDefault investment/sand cast, no post-heat-treatment | Default form for valve trim, nozzles, pump and hot-work parts; best balance of toughness and wear resistance. | 495 | 710 | 9 | 32 HRC | 2 % IACS |
Hot isostatic pressed | Pick when near-net-shape parts need fine uniform carbides, isotropic properties and no casting porosity. | 640 | 950 | 16 | 34 HRC | 2 % IACS |
Solution treated + aged | Select when maximum hardness and creep/wear resistance are wanted and reduced ductility is acceptable. | 650 | 900 | 4 | 40 HRC | 2.1 % IACS |
hot rolled / forged and annealed bar | Choose for wrought bar or forgings needing higher strength, ductility and sounder structure than castings. | 700 | 1,000 | 14 | 35 HRC | 2.1 % IACS |
What is Stellite 21 As Welded?
Stellite 21 As Welded is Stellite 21 supplied in the As Welded condition — use for cladding valve seats, dies and shafts; hardness rises substantially by work hardening in service. Stellite 21 As Welded has a yield strength of 490 MPa (71.1 ksi) and a tensile strength of 700 MPa (102 ksi) — weaker than 69% of cobalt-chrome alloy grades. Elongation at break is 8% and the elastic modulus is 248 GPa (36 Msi). Stellite 21 As Welded has a density of 8.33 g/cm³ (0.301 lb/in³), lighter than 64% of cobalt-chrome alloy grades. It melts at 1,186°C (2,167 °F). As Cast is the default condition FabDigit quotes; As Welded is available on request or by drawing note.
Advantages
- Low embodied carbon — 10 kg CO₂/kg, better than 82% of cobalt-chrome alloy grades
- Readily welded — 55/100, better than 80% of cobalt-chrome alloy grades
- Forms and bends easily — 20/100, better than 77% of cobalt-chrome alloy grades
Stellite 21 As Welded properties
Typical room-temperature values for Stellite 21 As Welded; 21 are specific to this condition. Other listed values are Stellite 21 reference data and may not represent this condition. Bars are the position among cobalt-chrome alloy grades.
Physical3
Stellite 21 As Welded has a density of 8.33 g/cm³ (0.301 lb/in³), lighter than 64% of cobalt-chrome alloy grades. It melts at 1,186°C (2,167 °F).
Mechanical16
Stellite 21 As Welded has a yield strength of 490 MPa (71.1 ksi) and a tensile strength of 700 MPa (102 ksi) — weaker than 69% of cobalt-chrome alloy grades. Elongation at break is 8% and the elastic modulus is 248 GPa (36 Msi).
Thermal6
Stellite 21 As Welded is rated for continuous service to 760°C (1,400 °F). It conducts heat at 14.8 W/m·K (8.55 BTU/hr·ft·°F), better than 84% of cobalt-chrome alloy grades. Thermal expansion is 14.2 µm/m·K (7.89 µin/in·°F).
Electrical3
Stellite 21 As Welded conducts electricity at 2 % IACS, better than 79% of cobalt-chrome alloy grades.
Chemical & Environmental3
Corrosion resistance is very good (78/100), better than 54% of cobalt-chrome alloy grades.
Sustainability4
Producing a kilogram of Stellite 21 As Welded takes about 145 MJ of energy and emits 10 kg of CO₂ — less than 73% of cobalt-chrome alloy grades. Typical recycled content is 25%.
Manufacturability8
Stellite 21 As Welded's machinability is not recommended (12/100, better than 61% of cobalt-chrome alloy grades); weldability good (55/100); formability poor (20/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Stellite 21 As Welded
Is Stellite 21 easy to machine?
Very difficult and work-hardening — use rigid setups, negative-rake carbide or CBN at low speed with heavy positive feed, or finish by grinding/EDM.
Can Stellite 21 be welded?
The most weldable Stellite: GTAW/PTA/SMAW with 250–500 °C preheat, low dilution, slow cooling; avoid interpass cracking on thick sections.
Can Stellite 21 be formed, bent or molded?
Practically no cold formability — produce by investment casting, HIP powder consolidation, hot forging above ~1050 °C, or weld overlay/AM.
What surface finishes work on Stellite 21?
Not anodizable; passivate or electropolish, and it takes a mirror polish for valve seats and implant surfaces; hard coatings rarely needed.
Stellite 21 chemical composition (wt %)
Limits by weight percent from the governing specification, written the way the spec states them — a single maximum for impurities, a range for alloying elements, and the base element as balance. Nominal is the typical mid-range value.
| Element | Spec limit (wt %) | Nominal |
|---|---|---|
| Clow carbon vs Stellite 6/12 → tougher, weldable | 0.2 – 0.35 | 0.25 |
| Cr | 25 – 29 | 27 |
| Mosolid-solution strengthener | 4.5 – 6 | 5.5 |
| Ni | 1.75 – 3.75 | 2.5 |
| Fe | ≤ 3 | 1 |
| Si | ≤ 1 | 0.6 |
| Mn | ≤ 1 | 0.6 |
| Wmax, incidental | ≤ 0.5 | — |
| Cobalance, ~60–63 % | balance | — |
Stellite 21 As Welded — frequently asked
What is Stellite 21 As Welded used for?
Stellite 21 As Welded is typically used for hot forging dies, pump shafts and sleeves, valve seats and trim, weld-overlay hardfacing on steel substrates, cast surgical implant components and hot shear and trim blades. In short: tougher hardfacing cobalt.
What is the yield strength of Stellite 21 As Welded?
Stellite 21 As Welded has a typical yield strength of 490 MPa (71.1 ksi) and a tensile strength of 700 MPa (102 ksi) — weaker than 69% of cobalt-chrome alloy grades. Strength varies by condition: see the 5 listed tempers.
Is Stellite 21 As Welded easy to machine?
Not especially — machinability is rated not recommended (12/100, better than 61% of cobalt-chrome alloy grades). Very difficult and work-hardening — use rigid setups, negative-rake carbide or CBN at low speed with heavy positive feed, or finish by grinding/EDM.
Can Stellite 21 As Welded be welded?
Yes — weldability is rated good (55/100). The most weldable Stellite: GTAW/PTA/SMAW with 250–500 °C preheat, low dilution, slow cooling; avoid interpass cracking on thick sections.
What surface finishes work on Stellite 21 As Welded?
Not anodizable; passivate or electropolish, and it takes a mirror polish for valve seats and implant surfaces; hard coatings rarely needed.
Can Stellite 21 As Welded be formed, bent or molded?
Practically no cold formability — produce by investment casting, HIP powder consolidation, hot forging above ~1050 °C, or weld overlay/AM.
What is the maximum service temperature of Stellite 21 As Welded?
Stellite 21 As Welded is rated for continuous use to about 760°C (1,400 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between Stellite 21 As Cast and Stellite 21 Aged?
As Cast is the default condition — default form for valve trim, nozzles, pump and hot-work parts; best balance of toughness and wear resistance. Aged: select when maximum hardness and creep/wear resistance are wanted and reduced ductility is acceptable. Yield strength is 495 MPa in As Cast versus 650 MPa in Aged.
Sources
- Stellite 21 alloy data sheet — Kennametal Stellite (2023)
- AMS 5385 — Cobalt Alloy Castings, Corrosion and Heat Resistant (Co-27Cr-5.5Mo-2.5Ni) — SAE International (2019)
- ASTM A494/A494M — Castings, Nickel and Nickel Alloy (related Co-Cr-Mo grades) — ASTM (2022)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys (Cobalt-base alloys) — ASM International (1990)
- ASM Handbook Vol. 13B — Corrosion: Materials — ASM International (2005)
Property data is compiled from published supplier and standards handbooks and normalised for comparison. Nothing on this page is a certification — request mill certs, CoC or material test reports with your order.