Cobalt-Chrome Alloy G-CoCr28 PM-HIP
Heat-treated state
UNS R30075 · EN 2.4778 · ISO 5832-4
PM-HIP = powder metallurgy, hot isostatically pressed
Highest strength and ductility route: fine equiaxed grains and dispersed carbides give near-double yield strength versus as-cast.
Values for the PM-HIP condition
Other G-CoCr28 tempers and conditions
G-CoCr28 is listed in 5 conditions; see the grade overview at G-CoCr28.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
FDefault As fabricated | Standard supply condition for cast implant and dental components; carbide-strengthened dendritic structure, maximum wear resistance, lowest ductility. | 500 | 720 | 9 | 30 HRC | — |
Cast + solution annealed | Choose when ductility and homogeneity matter more than peak hardness; dissolves interdendritic M23C6 carbides and reduces coring. | 520 | 760 | 15 | 27 HRC | 2 % IACS |
Hot isostatic pressed | Use for fatigue-critical cast implants: HIP closes shrinkage porosity and roughly doubles the endurance limit. | 560 | 900 | 18 | 32 HRC | 2 % IACS |
laser powder bed fusion, as-built + stress relieved | Additively manufactured dental frameworks and porous implant structures; very fine cellular structure gives high strength but anisotropy and residual stress require stress relief (HIP optional). | 800 | 1,200 | 12 | 40 HRC | 2 % IACS |
PM-HIPThis page Powder metallurgy, hot isostatically pressed | Highest strength and ductility route: fine equiaxed grains and dispersed carbides give near-double yield strength versus as-cast. | 840 | 1,250 | 20 | 40 HRC | 2 % IACS |
What is G-CoCr28 PM-HIP?
G-CoCr28 PM-HIP is G-CoCr28 heat treated to PM-HIP — highest strength and ductility route: fine equiaxed grains and dispersed carbides give near-double yield strength versus as-cast. G-CoCr28 PM-HIP has a yield strength of 840 MPa (122 ksi) and a tensile strength of 1,250 MPa (181 ksi) — stronger than 81% of cobalt-chrome alloy grades. Elongation at break is 20% and the elastic modulus is 230 GPa (33.4 Msi). G-CoCr28 PM-HIP has a density of 8.3 g/cm³ (0.3 lb/in³), lighter than 80% of cobalt-chrome alloy grades. It melts at 1,330°C (2,426 °F). F is the default condition FabDigit quotes; PM-HIP is available on request or by drawing note.
Advantages
- Good corrosion resistance — 92/100, better than 100% of cobalt-chrome alloy grades
- Polishes to a fine finish — 92/100, better than 93% of cobalt-chrome alloy grades
- Tough — resists crack growth — 78 MPa·√m (71 ksi·√in), better than 89% of cobalt-chrome alloy grades
- High strength — 840 MPa (122 ksi), better than 81% of cobalt-chrome alloy grades
- Ductile — tolerates forming and impact — 20%, better than 78% of cobalt-chrome alloy grades
G-CoCr28 PM-HIP properties
Typical room-temperature values for G-CoCr28 PM-HIP; 22 are specific to this condition. Other listed values are G-CoCr28 reference data and may not represent this condition. Bars are the position among cobalt-chrome alloy grades.
Physical3
G-CoCr28 PM-HIP has a density of 8.3 g/cm³ (0.3 lb/in³), lighter than 80% of cobalt-chrome alloy grades. It melts at 1,330°C (2,426 °F).
Mechanical15
G-CoCr28 PM-HIP has a yield strength of 840 MPa (122 ksi) and a tensile strength of 1,250 MPa (181 ksi) — stronger than 81% of cobalt-chrome alloy grades. Elongation at break is 20% and the elastic modulus is 230 GPa (33.4 Msi).
Thermal6
G-CoCr28 PM-HIP is rated for continuous service to 600°C (1,112 °F). It conducts heat at 14 W/m·K (8.09 BTU/hr·ft·°F), worse than 55% of cobalt-chrome alloy grades. Thermal expansion is 13.5 µm/m·K (7.5 µin/in·°F).
Electrical3
G-CoCr28 PM-HIP conducts electricity at 2 % IACS, better than 79% of cobalt-chrome alloy grades.
Chemical & Environmental3
Corrosion resistance is excellent (92/100), better than 100% of cobalt-chrome alloy grades.
Sustainability4
Producing a kilogram of G-CoCr28 PM-HIP takes about 145 MJ of energy and emits 11 kg of CO₂ — less than 73% of cobalt-chrome alloy grades. Typical recycled content is 20%.
Manufacturability8
G-CoCr28 PM-HIP's machinability is not recommended (12/100, better than 61% of cobalt-chrome alloy grades); weldability poor (30/100); formability not recommended (12/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with G-CoCr28 PM-HIP
Is G-CoCr28 easy to machine?
Very difficult: use rigid setups, positive-rake carbide or ceramic tooling, low speed (15–30 m/min carbide) with heavy constant feed and flood coolant to avoid dwelling in the work-hardened layer; grinding and EDM are common for finishing implant geometries.
Can G-CoCr28 be welded?
Best joined by laser or electron-beam welding with tight heat input; TIG possible on solution-annealed material with matching filler, but cast carbide networks and porosity promote hot cracking — post-weld solution anneal/HIP recommended.
Can G-CoCr28 be formed, bent or molded?
Investment (lost-wax) casting in vacuum or argon at ~1450–1500 °C pour temperature is the standard route; alloy is essentially not cold formable, so complex shapes come from casting, PM-HIP or laser powder bed fusion.
What surface finishes work on G-CoCr28?
Not anodizable — passivate in nitric acid per ASTM F86, electropolish, then diamond/alumina polish bearing surfaces to Ra ≤0.05 µm; porous or HA plasma-spray coatings are applied to fixation surfaces.
G-CoCr28 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 |
|---|---|---|
| Cr | 27 – 30 | 28.5 |
| Mo | 5 – 7 | 6 |
| NiISO 5832-4 limits Ni ≤1.0; F75 ≤0.50 | ≤ 0.5 | 0.2 |
| Fe | ≤ 0.75 | 0.3 |
| Ccarbide former, controls hardness/wear | ≤ 0.35 | 0.25 |
| Si | ≤ 1 | 0.6 |
| Mn | ≤ 1 | 0.6 |
| N | ≤ 0.25 | 0.1 |
| W | ≤ 0.2 | — |
| Al | ≤ 0.1 | — |
| Ti | ≤ 0.1 | — |
| B | ≤ 0.01 | — |
| P | ≤ 0.02 | — |
| S | ≤ 0.01 | — |
| Cobalance, ~62–65 % | balance | — |
G-CoCr28 PM-HIP — frequently asked
What is G-CoCr28 PM-HIP used for?
G-CoCr28 PM-HIP is typically used for hip implants, dental crowns and bridges and cast surgical components. In short: cast ASTM F75 equivalent; investment-cast implant alloy; casting and L-PBF routes.
What is the yield strength of G-CoCr28 PM-HIP?
G-CoCr28 PM-HIP has a typical yield strength of 840 MPa (122 ksi) and a tensile strength of 1,250 MPa (181 ksi) — stronger than 81% of cobalt-chrome alloy grades. Strength varies by condition: see the 5 listed tempers.
Is G-CoCr28 PM-HIP easy to machine?
Not especially — machinability is rated not recommended (12/100, better than 61% of cobalt-chrome alloy grades). Very difficult: use rigid setups, positive-rake carbide or ceramic tooling, low speed (15–30 m/min carbide) with heavy constant feed and flood coolant to avoid dwelling in the work-hardened layer; grinding and EDM are common for finishing implant geometries.
Can G-CoCr28 PM-HIP be welded?
Not readily — weldability is rated poor (30/100). Best joined by laser or electron-beam welding with tight heat input; TIG possible on solution-annealed material with matching filler, but cast carbide networks and porosity promote hot cracking — post-weld solution anneal/HIP recommended.
What surface finishes work on G-CoCr28 PM-HIP?
Not anodizable — passivate in nitric acid per ASTM F86, electropolish, then diamond/alumina polish bearing surfaces to Ra ≤0.05 µm; porous or HA plasma-spray coatings are applied to fixation surfaces.
Can G-CoCr28 PM-HIP be formed, bent or molded?
Investment (lost-wax) casting in vacuum or argon at ~1450–1500 °C pour temperature is the standard route; alloy is essentially not cold formable, so complex shapes come from casting, PM-HIP or laser powder bed fusion.
What is the maximum service temperature of G-CoCr28 PM-HIP?
G-CoCr28 PM-HIP is rated for continuous use to about 600°C (1,112 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between G-CoCr28-F and G-CoCr28 PM-HIP?
F is the default condition — standard supply condition for cast implant and dental components; carbide-strengthened dendritic structure, maximum wear resistance, lowest ductility. PM-HIP: highest strength and ductility route: fine equiaxed grains and dispersed carbides give near-double yield strength versus as-cast. Yield strength is 500 MPa in F versus 840 MPa in PM-HIP.
Sources
- ASTM F75 — Standard Specification for Cobalt-28 Chromium-6 Molybdenum Alloy Castings and Casting Alloy for Surgical Implants (UNS R30075) — ASTM International (2018)
- ISO 5832-4 — Implants for surgery — Metallic materials — Part 4: Cobalt-chromium-molybdenum casting alloy — ISO (2014)
- ASTM F1537 — Wrought Cobalt-28Chromium-6Molybdenum Alloys for Surgical Implants — ASTM International (2020)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys (Cobalt and Cobalt Alloys) — ASM International (1990)
- Handbook of Materials for Medical Devices / Biomaterials Science — ASM International / Elsevier (2003)
- CoCrMo (F75) investment casting and PM-HIP alloy datasheets — specialty implant alloy producers (2023)
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.