CoCrMo Bar – ASTM F1537 Cobalt Chrome Moly Round Bar (Co-28Cr-6Mo)
CoCrMo bar – also called cobalt chrome moly round bar or Co-28Cr-6Mo – is a wrought cobalt-chromium-molybdenum alloy bar made to ASTM F1537 and ISO 5832-12. ASC LLP, Mumbai, supplies CoCrMo round bar in low-carbon (UNS R31537) and high-carbon (UNS R31538) grades, in annealed, hot-worked and warm-worked conditions, with EN 10204 3.1 mill certificates.
What is CoCrMo Bar?
CoCrMo is a cobalt-base alloy with about 28% chromium and 6% molybdenum. It combines high strength, excellent wear resistance and very good corrosion resistance, and it is non-magnetic. These properties make wrought CoCrMo bar a standard material for orthopaedic and dental implant components, as well as for wear-resistant precision parts.
CoCrMo Round Bar – Quick Facts
- Alloy: Co-28Cr-6Mo, UNS R31537 (low carbon), R31538 (high carbon), R31539 (dispersion-strengthened)
- Specifications: ASTM F1537, ISO 5832-12; forgings to ASTM F799
- Conditions: annealed, hot-worked or warm-worked
- Form: round bar, centreless-ground or turned; cut lengths on request
- Certificate: EN 10204 3.1 with heat number, chemistry and tensile results
CoCrMo Alloys Covered by ASTM F1537
| Alloy (ASTM F1537) | UNS | Carbon | Main feature |
| Alloy 1 – low carbon (LC) | R31537 | 0.14% max | Best ductility; most common bar grade |
| Alloy 2 – high carbon (HC) | R31538 | 0.15 – 0.35% | Carbides add wear resistance – bearing and articulating surfaces |
| Alloy 3 – dispersion-strengthened | R31539 | 0.14% max | Small aluminium and lanthanum additions refine grain size |
Key Properties of CoCrMo Bar
- High strength: up to 1,172 MPa minimum tensile in the warm-worked condition.
- Wear resistance: one of the most wear-resistant implant alloys, especially the high-carbon grade.
- Corrosion resistance: a stable chromium-oxide film resists body fluids and many chloride environments.
- Stiffness: elastic modulus about twice that of titanium alloys.
- Non-magnetic in the wrought condition.
Applications of CoCrMo Round Bar
- Orthopaedic implants: femoral heads, hip stems, knee femoral components, spinal rods and connectors.
- Dental: implant abutments, frameworks and attachments.
- Surgical instruments and other medical-device components that need wear resistance.
- Industrial: wear-resistant pins, bushings, valve and pump parts, and precision components where cobalt-chrome hardness and corrosion resistance are needed.
Note: ASC LLP supplies certified CoCrMo bar stock. Qualification of any medical device made from it remains the responsibility of the device manufacturer. For high-strength cobalt-nickel bar for bolting and springs, see MP35N bars.
Technical Details of CoCrMo ASTM F1537 Round Bar
CoCrMo Round Bar Sizes & Weight Chart
| Diameter (mm) | Weight (kg/m) | Diameter (mm) | Weight (kg/m) |
| 6 | 0.23 | 20 | 2.61 |
| 8 | 0.42 | 25 | 4.07 |
| 10 | 0.65 | 30 | 5.87 |
| 12 | 0.94 | 40 | 10.43 |
| 16 | 1.67 | 50 | 16.30 |
Weights calculated at a density of 8.3 g/cm³. Inch sizes, tolerances (e.g. h7 / h9 ground) and cut lengths on request.
ASTM F1537 Mechanical Properties
| Condition (ASTM F1537) | Tensile strength (min) | 0.2% yield strength (min) | Elongation (min) |
| Annealed | 897 MPa (130 ksi) | 517 MPa (75 ksi) | 20% |
| Hot-worked | 1,000 MPa (145 ksi) | 700 MPa (101 ksi) | 12% |
| Warm-worked | 1,172 MPa (170 ksi) | 827 MPa (120 ksi) | 12% |
Minimum values per ASTM F1537. Actual results are shown on the mill certificate for each heat.
Specifications for Cobalt Chrome Moly Bar
| Standard | Scope |
| ASTM F1537 | Wrought Co-28Cr-6Mo alloys for surgical implants – bar, rod and wire (UNS R31537, R31538, R31539) |
| ISO 5832-12 | Implants for surgery – wrought cobalt-chromium-molybdenum alloy (ISO equivalent of F1537) |
| ASTM F799 | Co-28Cr-6Mo alloy forgings for surgical implants |
| ASTM F75 | Co-28Cr-6Mo castings and casting alloy (UNS R30075) |
| ASTM F562 | MP35N – wrought Co-35Ni-20Cr-10Mo alloy (UNS R30035), a different cobalt alloy |
Ultrasonic testing to AMS 2630 or a customer procedure can be arranged on request.
CoCrMo Bar Supply Conditions
| Condition | How it is produced | Typical choice |
| Annealed | Solution-annealed after working; lowest strength, highest ductility | Parts that are bent, formed or heavily machined |
| Hot-worked | Finished by hot working; higher strength | General implant components |
| Warm-worked | Finished by warm working; highest strength | Highly loaded stems, rods and fixation parts |
F1537 alloys are not age-hardened; strength comes from working and carbon content.
CoCrMo Chemical Composition (ASTM F1537)
| Element (wt %) | Alloy 1 (R31537) | Alloy 2 (R31538) |
| Chromium (Cr) | 26.0 – 30.0 | 26.0 – 30.0 |
| Molybdenum (Mo) | 5.0 – 7.0 | 5.0 – 7.0 |
| Carbon (C) | 0.14 max | 0.15 – 0.35 |
| Nickel (Ni) | 1.0 max | 1.0 max |
| Iron (Fe) | 0.75 max | 0.75 max |
| Manganese (Mn) | 1.0 max | 1.0 max |
| Silicon (Si) | 1.0 max | 1.0 max |
| Nitrogen (N) | 0.25 max | 0.25 max |
| Cobalt (Co) | Balance | Balance |
CoCrMo Physical Properties
| Property (approx.) | Value |
| Density | 8.3 g/cm³ |
| Modulus of elasticity | ≈ 220 – 240 GPa |
| Melting range | ≈ 1,290 – 1,360 °C |
| Thermal conductivity | ≈ 13 W/m·K |
| Magnetic | Non-magnetic |
CoCrMo vs MP35N vs Titanium Bar
| Property | CoCrMo (F1537) | MP35N (F562) | Ti-6Al-4V ELI |
| Base | Cobalt-chromium-molybdenum | Cobalt-nickel-chromium-molybdenum | Titanium |
| Density (approx.) | 8.3 g/cm³ | 8.4 g/cm³ | 4.4 g/cm³ |
| Modulus (approx.) | 220 – 240 GPa | ≈ 230 GPa | ≈ 110 GPa |
| Nickel content | 1% max | ≈ 35% | None |
| Strengths | Wear resistance, stiffness | Very high strength after cold work + ageing | Light weight, lower stiffness |
Choose CoCrMo where wear resistance and stiffness matter, MP35N for very high-strength bolting and springs, and titanium bar where low weight and lower stiffness are wanted. More background: ASTM F1537 round bars explained.
Why Choose ASC LLP for CoCrMo Bar?
- Correct specification: bar certified to ASTM F1537 and / or ISO 5832-12, low or high carbon, in the condition you specify.
- Full traceability: EN 10204 3.1 certificates with heat number, chemistry and tensile results; third-party inspection on request.
- Cut to size: small quantities and cut lengths for prototypes and machining runs.
- Related alloys: MP35N, titanium and other high-performance bars from one supplier.
- Export packing and documentation for shipments worldwide.
Send grade, condition, diameter and quantity to sales@amardeepsteel.com or call 022-67439130.
Frequently Asked Questions – CoCrMo Bar
What is CoCrMo bar?
CoCrMo bar is wrought cobalt-chromium-molybdenum alloy bar, typically Co-28Cr-6Mo, made to ASTM F1537 or ISO 5832-12. It is known for high strength, wear resistance and corrosion resistance and is widely used for implant and wear-resistant components.
What is the difference between R31537 and R31538?
Both are ASTM F1537 Co-28Cr-6Mo alloys. R31537 (Alloy 1) is low carbon with 0.14% max carbon and better ductility. R31538 (Alloy 2) is high carbon with 0.15–0.35% carbon, which forms carbides for extra wear resistance.
What are the ASTM F1537 mechanical properties?
Minimums are 897 MPa tensile, 517 MPa yield and 20% elongation in the annealed condition; 1,000 MPa, 700 MPa and 12% hot-worked; and 1,172 MPa, 827 MPa and 12% warm-worked.
What is the difference between ASTM F1537, F799 and F75?
ASTM F1537 covers wrought Co-28Cr-6Mo bar, rod and wire; ASTM F799 covers forgings of the same alloy; ASTM F75 covers castings. ISO 5832-12 is the ISO equivalent of F1537.
Is CoCrMo the same as MP35N?
No. CoCrMo (ASTM F1537) contains 1% nickel maximum, while MP35N (ASTM F562, UNS R30035) contains about 35% nickel. MP35N is used mainly where very high strength is needed, such as bolting and springs.
Is CoCrMo magnetic?
No. Wrought CoCrMo alloy to ASTM F1537 is non-magnetic.
Global Reach
ASC LLP supplies high-performance alloy bars to customers in the USA, Europe, the Middle East and Asia, with secure packing and full documentation. Buyers worldwide rely on our CoCrMo ASTM F1537 round bar for certified material and traceability.
Countries We Export To
UNITED STATES, EUROPE, UK, UAE, SAUDI ARABIA, OMAN, KUWAIT, JORDAN, QATAR, INDONESIA, MALAYSIA, BRAZIL, SPAIN, ITALY, FRANCE, GERMANY, BAHRAIN, SRI LANKA, AZERBAIJAN, AUSTRALIA, AUSTRIA, PHILIPPINES, TURKEY, RUSSIA, IRAN, IRAQ, CANADA, KOREA, JAPAN, YEMEN, FINLAND, ZIMBABWE, HUNGARY, PORTUGAL, VIETNAM, MOROCCO, THAILAND, SOUTH AFRICA, MEXICO, SINGAPORE, GREECE, KUWAIT, POLAND, NEW ZEALAND, SWEDEN, SWITZERLAND, BELGIUM, BHUTAN, BANGLADESH, TAIWAN, ROMANIA, CAMBODIA, KAZAKHSTAN, AFGHANISTAN.
