Cobalt-Chrome Alloy Stellite 21-HIP (Hot isostatic pressed)
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UNS R30021 · also CoCrMo Stellite
Pick when near-net-shape parts need fine uniform carbides, isotropic properties and no casting porosity.
Values for the HIP condition
Other Stellite 21 tempers and conditions
Stellite 21 is listed in 5 conditions; see the grade overview at Stellite 21.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
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 |
HIPThis page 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-HIP?
Stellite 21-HIP is Stellite 21 in the HIP condition — pick when near-net-shape parts need fine uniform carbides, isotropic properties and no casting porosity. Stellite 21-HIP has a yield strength of 640 MPa (92.8 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 77% of cobalt-chrome alloy grades. Elongation at break is 16% and the elastic modulus is 250 GPa (36.3 Msi). Stellite 21-HIP 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; HIP is available on request or by drawing note.
Advantages
- Readily welded — 58/100, better than 89% of cobalt-chrome alloy grades
- Tough — resists crack growth — 70 MPa·√m (63.7 ksi·√in), better than 82% of cobalt-chrome alloy grades
- Forms and bends easily — 25/100, better than 82% of cobalt-chrome alloy grades
- Low embodied carbon — 10 kg CO₂/kg, better than 82% of cobalt-chrome alloy grades
Stellite 21-HIP properties
Typical room-temperature values for Stellite 21-HIP; 22 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-HIP 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-HIP has a yield strength of 640 MPa (92.8 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 77% of cobalt-chrome alloy grades. Elongation at break is 16% and the elastic modulus is 250 GPa (36.3 Msi).
Thermal6
Stellite 21-HIP 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-HIP conducts electricity at 2 % IACS, better than 79% of cobalt-chrome alloy grades.
Chemical & Environmental3
Corrosion resistance is very good (82/100), better than 70% of cobalt-chrome alloy grades.
Sustainability4
Producing a kilogram of Stellite 21-HIP 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-HIP's machinability is poor (16/100, better than 86% of cobalt-chrome alloy grades); weldability good (58/100); formability poor (25/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with Stellite 21-HIP
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-HIP — frequently asked
What is Stellite 21-HIP used for?
Stellite 21-HIP 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-HIP?
Stellite 21-HIP has a typical yield strength of 640 MPa (92.8 ksi) and a tensile strength of 950 MPa (138 ksi) — stronger than 77% of cobalt-chrome alloy grades. Strength varies by condition: see the 5 listed tempers.
Is Stellite 21-HIP easy to machine?
Not especially — machinability is rated poor (16/100, better than 86% 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-HIP be welded?
Yes — weldability is rated good (58/100). 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-HIP?
Not anodizable; passivate or electropolish, and it takes a mirror polish for valve seats and implant surfaces; hard coatings rarely needed.
Can Stellite 21-HIP 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-HIP?
Stellite 21-HIP 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.