Cobalt-Chrome Alloy F75 · heat-treated state
Cobalt-Chrome Alloy F75 Stress Relieved
Properties of the Stress Relieved condition, compared with the other F75 tempers.
Standard post-print treatment for laser-melted CoCrMo: removes residual stress and prevents distortion while keeping most as-printed strength.
What is F75 Stress Relieved?
F75 Stress Relieved is F75 heat treated to Stress Relieved — standard post-print treatment for laser-melted CoCrMo: removes residual stress and prevents distortion while keeping most as-printed strength. F75 Stress Relieved has a yield strength of 820 MPa (119 ksi) and a tensile strength of 1,150 MPa (167 ksi) — stronger than 74% of cobalt-chrome alloy grades. Elongation at break is 15% and the elastic modulus is 210 GPa (30.5 Msi). F75 Stress Relieved has a density of 8.3 g/cm³ (0.3 lb/in³), lighter than 81% of cobalt-chrome alloy grades. It melts at 1,330°C (2,426 °F). As Cast is the default condition FabDigit quotes; Stress Relieved is available on request or by drawing note.
Advantages
- Good corrosion resistance — 88/100, better than 84% of cobalt-chrome alloy grades
- Ductile — tolerates forming and impact — 15%, better than 75% of cobalt-chrome alloy grades
F75 Stress Relieved properties
Typical room-temperature values for F75 Stress Relieved — 10 properties are specific to this condition; the rest are grade-level values shared by every F75 temper. Each bar shows where the value sits among the cobalt-chrome alloy grades in FabDigit's library — further right is higher.
Physical3
F75 Stress Relieved has a density of 8.3 g/cm³ (0.3 lb/in³), lighter than 81% of cobalt-chrome alloy grades. It melts at 1,330°C (2,426 °F).
Mechanical16
F75 Stress Relieved has a yield strength of 820 MPa (119 ksi) and a tensile strength of 1,150 MPa (167 ksi) — stronger than 74% of cobalt-chrome alloy grades. Elongation at break is 15% and the elastic modulus is 210 GPa (30.5 Msi).
Thermal6
F75 Stress Relieved 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 53% of cobalt-chrome alloy grades. Thermal expansion is 13 µm/m·K (7.22 µin/in·°F).
Electrical3
F75 Stress Relieved conducts electricity at 1.9 % IACS, worse than 54% of cobalt-chrome alloy grades.
Chemical & Environmental3
Corrosion resistance is excellent (88/100), better than 84% of cobalt-chrome alloy grades.
Sustainability4
Producing a kilogram of F75 Stress Relieved takes about 150 MJ of energy and emits 11 kg of CO₂ — less than 60% of cobalt-chrome alloy grades. Typical recycled content is 25%.
Manufacturability8
F75 Stress Relieved's machinability is not recommended (11/100, better than 59% of cobalt-chrome alloy grades); weldability poor (25/100); formability not recommended (10/100).
Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.
Other F75 tempers and conditions
F75 is also supplied in 6 other conditions. The full side-by-side table is on the F75 overview.
- As CastDefaultDefault condition for investment-cast implant and dental components; meets ASTM F75 minimums with coarse dendritic structure and interdendritic carbides.510 MPa yield · 30 HRC
- As PrintedAs-built laser powder-bed condition: very fine cellular structure gives the highest strength and hardness of any F75 form, but with residual stress and anisotropy.900 MPa yield · 40 HRC
- pressure_sinteredPowder-metallurgy Co-28Cr-6Mo consolidated by uniaxial hot pressing / pressure-assisted sintering to near-full density, giving a fine equiaxed grain structure with markedly higher strength and ductility than the cast alloy.840 MPa yield · 36 HRC
- Stress RelievedStandard post-print treatment for laser-melted CoCrMo: removes residual stress and prevents distortion while keeping most as-printed strength.820 MPa yield · 37 HRC
- HIPPick for load-bearing implants and critical AM parts: closes porosity and lack-of-fusion defects, giving the best ductility, toughness and fatigue life.650 MPa yield · 32 HRC
- heat_treated_castInvestment-cast Co-28Cr-6Mo (R30075) given a post-cast homogenizing/solution heat treatment that dissolves interdendritic carbides and raises ductility over the as-cast state while keeping the coarse cast grain structure.560 MPa yield · 31 HRC
- Solution AnnealedChoose when carbide dissolution and higher ductility/uniformity are needed before final machining or forming of cast or AM parts.520 MPa yield · 28 HRC
Working with F75 Stress Relieved
Is F75 easy to machine?
Rigid setups, sharp positive-rake carbide or ceramic tools, low speed (15–30 m/min carbide) with heavy constant feed and flood coolant — never dwell, the alloy work-hardens instantly; grinding and EDM are common for finished implant geometry.
Can F75 be welded?
Cast high-carbon F75 is prone to hot cracking; use low-heat GTAW/laser/electron-beam with matching Co-Cr filler, preheat and post-weld solution treatment, or design to avoid welding altogether.
Can F75 be formed, bent or molded?
Not cold formable — parts are investment cast, laser powder-bed printed or milled from HIPed blanks; AM builds need supports, 750–1150 °C stress relief and optional HIP.
What surface finishes work on F75?
Sand/blast, then belt and diamond/alumina polish to a mirror bearing surface (Ra ≤ 0.02 µm); passivate or electropolish for biocompatibility; DLC/TiN PVD used for extra wear life. No anodizing.
F75 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 |
|---|---|---|
| Crpassive film former | 27 – 30 | 28.5 |
| Mosolid-solution strengthening, pitting resistance | 5 – 7 | 6 |
| Niimpurity limit (allergy control) | ≤ 0.5 | 0.2 |
| Fe | ≤ 0.75 | 0.3 |
| Clow-carbon AM powders typically ≤0.16 | ≤ 0.35 | 0.25 |
| Si | ≤ 1 | 0.6 |
| Mn | ≤ 1 | 0.6 |
| W | ≤ 0.2 | — |
| N | ≤ 0.25 | — |
| Al | ≤ 0.1 | — |
| Ti | ≤ 0.1 | — |
| B | ≤ 0.01 | — |
| P | ≤ 0.02 | — |
| S | ≤ 0.01 | — |
| Cobalance, ≈62–65 % | balance | — |
F75 Stress Relieved — frequently asked
What is F75 Stress Relieved used for?
F75 Stress Relieved is typically used for hip femoral heads and stems, knee femoral components, dental crowns and bridges, partial denture frameworks, spinal implant components and wear-resistant bearing surfaces. In short: medical implant cobalt.
What is the yield strength of F75 Stress Relieved?
F75 Stress Relieved has a typical yield strength of 820 MPa (119 ksi) and a tensile strength of 1,150 MPa (167 ksi) — stronger than 74% of cobalt-chrome alloy grades. Strength varies by condition: see the 7 listed tempers.
Is F75 Stress Relieved easy to machine?
Not especially — machinability is rated not recommended (11/100, better than 59% of cobalt-chrome alloy grades). Rigid setups, sharp positive-rake carbide or ceramic tools, low speed (15–30 m/min carbide) with heavy constant feed and flood coolant — never dwell, the alloy work-hardens instantly; grinding and EDM are common for finished implant geometry.
Can F75 Stress Relieved be welded?
Not readily — weldability is rated poor (25/100). Cast high-carbon F75 is prone to hot cracking; use low-heat GTAW/laser/electron-beam with matching Co-Cr filler, preheat and post-weld solution treatment, or design to avoid welding altogether.
What surface finishes work on F75 Stress Relieved?
Sand/blast, then belt and diamond/alumina polish to a mirror bearing surface (Ra ≤ 0.02 µm); passivate or electropolish for biocompatibility; DLC/TiN PVD used for extra wear life. No anodizing.
Can F75 Stress Relieved be formed, bent or molded?
Not cold formable — parts are investment cast, laser powder-bed printed or milled from HIPed blanks; AM builds need supports, 750–1150 °C stress relief and optional HIP.
What is the maximum service temperature of F75 Stress Relieved?
F75 Stress Relieved 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 F75 As Cast and F75-HIP?
As Cast is the default condition — default condition for investment-cast implant and dental components; meets ASTM F75 minimums with coarse dendritic structure and interdendritic carbides. HIP: pick for load-bearing implants and critical AM parts: closes porosity and lack-of-fusion defects, giving the best ductility, toughness and fatigue life. Yield strength is 510 MPa in As Cast versus 650 MPa in HIP.
Can FabDigit make parts in F75 Stress Relieved?
Yes — F75 Stress Relieved is available for CNC machining and 3D printing with instant online pricing. Upload a STEP file to get a price and a DFM check.
Sources
- ASTM F75 — Standard Specification for Cobalt-28 Chromium-6 Molybdenum Alloy Castings and Casting Alloy for Surgical Implants — ASTM International (2018)
- ASTM F3301 — Additive Manufacturing, Post Processing Methods, Standard Specification for Thermal Post-Processing Metal Parts — ASTM International (2018)
- ASM Handbook Vol. 2 — Properties and Selection: Nonferrous Alloys (Cobalt-Base Alloys) — ASM International (1990)
- EOS CobaltChrome MP1 Material Data Sheet — EOS GmbH (2022)
- Sandvik Osprey CoCrMo (ASTM F75) AM Powder Datasheet — Sandvik (2022)
- Biomaterials property compilations for Co-Cr-Mo implant alloys — Springer / Elsevier reviews (2019)
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.