CoCrMo
metalcobalt-chromium alloy (biomedical and aerospace grade)
Cobalt-Chromium-MolybdenumUNS R30075ASTM F75 (casting equiv.)ISO 5832-12 (wrought equiv.)EOS Cobalt Chrome MP1Co-28Cr-6Mo
Composition — UNS R30075 / ASTM F3213-17
| Element | Min % | Max % | Notes |
|---|---|---|---|
| Co | bal. | balance | |
| Cr | 26.00 | 30.000 | Passivation layer (Cr₂O₃) — drives corrosion and oxidation resistance. Key for biocompatibility. |
| Mo | 5.00 | 7.000 | Solid solution strengthening and pitting corrosion resistance in chloride (body fluids) |
| Ni | — | 1.000 | |
| Fe | — | 0.750 | |
| C | — | 0.140 | M₂₃C₆ carbides form at grain boundaries — strengthening but potential sensitisation at elevated temperature |
| Si | — | 1.000 | |
| Mn | — | 1.000 | |
| N | — | 0.250 | Controlled nitrogen stabilises FCC matrix and improves corrosion resistance |
| W | — | 0.200 | Optional: some dental grades use W for additional solid solution strengthening |
| P | — | 0.020 | |
| S | — | 0.010 |
Mechanical & thermal properties — 3 conditions
| Property | LPBF as-built (XY) | LPBF as-built (Z) | LPBF solution-annealed (XY) |
|---|---|---|---|
| Elastic modulus | 195–220 GPa | — | — |
| Yield strength (0.2%) | 980–1200 MPa | 840–1080 MPa | 630–780 MPa |
| Ultimate tensile strength | 1200–1420 MPa | 1050–1270 MPa | 880–1080 MPa |
| Elongation at break | 2.0–6.0 % | 1.0–4.0 % | 8.0–18.0 % |
| Hardness (HV) | 380–480 HV10 | — | 270–340 HV10 |
| Fatigue strength | 430–580 MPa | — | — |
| Density | 8.29 g/cm³ | — | — |
| Thermal conductivity | 14.3 W/m·K | — | — |
| CTE | 12.8–14.0 µm/m·K | — | — |
| As-built surface Ra | 8.0–16.0 µm | — | — |
Values shown as min–max where a spread is reported, otherwise as typical ± unit. Ranges reflect inter-source variation, not single-sample scatter. All values are for AM-processed specimens unless noted.
Engineering considerations
- Biocompatibility testing: ASTM F3213 covers mechanical and compositional requirements but NOT biocompatibility. ISO 10993-1 cytotoxicity, sensitisation, and genotoxicity testing required for implantable devices.
- Wear debris: metal-on-metal bearing surfaces (CoCrMo-on-CoCrMo) are under increasing regulatory scrutiny (FDA 2016 guidance). Ceramic-on-CoCrMo or UHMWPE-on-CoCrMo reduces ion release.
- Surface finish for implants: Ra <0.8 µm for bone cement interfaces; Ra <0.05 µm (mirror polish) for articulating bearing surfaces. Electropolishing achieves Ra ~0.05 µm from as-built Ra ~12 µm.
- Lattice structures: CoCrMo LPBF lattices (300–600 µm pore size) achieve stiffness matching to trabecular bone (~0.5–3 GPa) — used for spinal cages and metaphyseal sleeves. Strut diameter minimum ~200 µm.
- Stress relief before part removal: minimum 1000°C/1h (vacuum) recommended to prevent distortion. Parts are highly susceptible to distortion if removed without stress relief.
- Post-heat-treatment decision: as-built provides optimal wear resistance (hardness 430 HV). Solution anneal (1150°C) improves ductility but sacrifices wear resistance. Choose based on application.
- Powder safety: cobalt powder is designated as a possible human carcinogen (IARC Group 2B). Vacuum or glove-box powder handling required. Mandatory COSHH assessment before any CoCrMo LPBF operation.
- Regulatory pathway (EU): Class III medical devices (joint replacements) require CE marking under EU MDR 2017/745 with Notified Body review. AM-specific process validation per ASTM F3407 or equivalent required.
Advantages
- Highest hardness of any standard AM biomedical metal — superior wear resistance for articulating surfaces
- Excellent corrosion resistance in physiological environments (body fluids, PBS, Ringer's solution)
- Biocompatible — ISO 10993 compliant; long clinical track record in cobalt alloy implants
- High fatigue strength (~500 MPa) — critical for cyclic-loaded implants (hip stems: ~3 million cycles/year)
- Strong high-temperature properties: retains significant strength to 900°C — aerospace turbine component use
- Outstanding creep resistance at moderate temperatures
- Excellent osseointegration potential when surface-roughened (Ra 1–3 µm for bone contact)
- Non-magnetic — MRI compatible implants possible
Limitations
- Very low as-built ductility (2.5–6%) — barely meets ASTM F3213 minimum; fatigue-critical implants need rigorous process control
- Ion release concern: Co²⁺ and Cr³⁺/Cr⁶⁺ ions released from wear debris — regulatory and clinical concern for metal-on-metal bearings
- Extremely high hardness makes post-machining difficult — hard turning tools, CBN inserts, slow cutting speeds required
- Dense (8.29 g/cm³) — heaviest common biomedical AM metal; hip implant weight matters for elderly patients
- Limited LPBF machine compatibility — requires high-power laser (≥400 W) and careful atmosphere control
- High residual tensile stress in as-built state — mandatory stress relief for fatigue-critical implants
- Powder handling: Co is classified as a potentially carcinogenic metal — strict COSHH/OSHA inhalation controls mandatory
- High cost: raw powder 4–6× more expensive than SS316L per kg
Typical applications
Orthopaedic implants — hip femoral heads, knee bearing tibial insertsDental frameworks, crowns, and bridges (metal-ceramic restorations)Spinal fusion cages and interbody devicesPatient-specific maxillofacial reconstruction platesSurgical instruments requiring high wear resistanceTurbine blades for industrial gas turbines (high-temperature aerospace grade)Rotary instruments (dental drills, cutting burs)Articulating joint surfaces requiring Ra <0.1 µmCustom orthopaedic implants with trabecular lattice structures
Industries
medicaldentalaerospace
Standards & certifications
ASTM-F3213established
CoCrMo (Co-28Cr-6Mo) parts produced by powder bed fusion — composition, powder, and minimum mechanical property requirements
medicaldentalaerospace
YS ≥827 MPa, UTS ≥1172 MPa, El ≥2.5% minimum. Implant parts additionally require ISO 10993 biocompatibility testing.
ISO-5832-12established
Wrought CoCrMo baseline for comparison with LPBF-produced implants
medical
Regulatory bodies (FDA, CE) require LPBF CoCrMo implants to meet or exceed ISO 5832-12 properties.
Compatible AM processes (2)
Other metal materials
Ti-6Al-4V Grade 5titanium alloy — alpha-beta316L Stainless Steelaustenitic stainless steel17-4PH Stainless Steelmartensitic precipitation-hardening stainless steelAlSi10Mgaluminium-silicon alloy (cast grade adapted for AM)AlSi7Mg Aluminium Alloyhypoeutectic Al-Si-Mg precipitation-hardenable aluminium alloyInconel 718nickel superalloy — precipitation-hardenedInconel 625nickel superalloy — solid-solution-strengthenedMaraging Steel MS1 (18Ni-300)maraging steel (ultra-high-strength, precipitation-hardened)H13 Tool Steelchromium-molybdenum hot-work tool steel
Related calculators
HT AdvisorStandard stress-relief, solution, and aging cycles for AM metals (Ti-6Al-4V, IN718, 17-4PH, AlSi10Mg, 316L, CuCrZr) per AMS, ASTM F3301, and AMS 5664.DistortionEstimate residual stress and distortion risk index (σ/σ_y) for LPBF and DED builds. Mercelis-Kruth model with preheat sensitivity table.VEDCompute LPBF VED from power, scan speed, hatch, and layer thickness. Includes process windows for common alloys.HIPRecommended HIP temperature, pressure, and dwell time for AM metals per ASTM F3301, AMS 2801, and DEF STAN 02-835. Covers Ti alloys, Ni superalloys, steels.FatigueS-N curve estimation for AM metals using the Basquin law. Accounts for surface roughness stress concentration (Kt from Ra), build direction anisotropy, and porosity factor.
Last reviewed: 2026-05-04 · v1 · Sources: ASTM-F3213, ISO-5832-12, eos-cochrmo-2023, murr-2012-cocr, santos-2012-cocr, debroy-2018-review, yadollahi-2017-fatigue, ASTM-E8, ASTM-E466, ISO-52904