Cobalt-Chrome Alloy F1537 Alloy 1-ANN (Annealed)
Heat-treated state · default condition
ASTM F1537 Alloy 1 · UNS R31537 · ISO 5832-12 Alloy 1
Most commonly stocked raw bar condition: maximum ductility for subsequent forging, machining or forming of implant components.
Values for the ANN condition
Other F1537 Alloy 1 tempers and conditions
F1537 Alloy 1 is listed in 3 conditions; see the grade overview at F1537 Alloy 1.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
ANNDefaultThis page Annealed | Most commonly stocked raw bar condition: maximum ductility for subsequent forging, machining or forming of implant components. | 610 | 1,000 | 35 | 29 HRC | — |
Hot Worked | Choose for near-net-shape forgings (stems, knee components) needing higher strength than annealed with still-good ductility. | 850 | 1,200 | 22 | 35 HRC | — |
Warm Worked | Highest-strength condition of Alloy 1 — pick for slender, highly loaded implants (femoral stems, spinal rods) where fatigue strength governs. | 1,050 | 1,400 | 18 | 42 HRC | — |
What is F1537 Alloy 1-ANN?
F1537 Alloy 1-ANN is F1537 Alloy 1 heat treated to ANN — most commonly stocked raw bar condition: maximum ductility for subsequent forging, machining or forming of implant components. F1537 Alloy 1-ANN has a yield strength of 610 MPa (88.5 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 58% of cobalt-chrome alloy grades. Elongation at break is 35% and the elastic modulus is 230 GPa (33.4 Msi). F1537 Alloy 1-ANN 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).
Advantages
- Good corrosion resistance — 92/100, better than 100% of cobalt-chrome alloy grades
- Tough — resists crack growth — 100 MPa·√m (91 ksi·√in), better than 97% of cobalt-chrome alloy grades
- Polishes to a fine finish — 92/100, better than 93% of cobalt-chrome alloy grades
- Forms and bends easily — 35/100, better than 86% of cobalt-chrome alloy grades
- Ductile — tolerates forming and impact — 35%, better than 85% of cobalt-chrome alloy grades
F1537 Alloy 1-ANN properties
Typical room-temperature values for F1537 Alloy 1-ANN; 18 are specific to this condition. Other listed values are F1537 Alloy 1 reference data and may not represent this condition. Bars are the position among cobalt-chrome alloy grades.
Physical3
F1537 Alloy 1-ANN 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).
Mechanical16
F1537 Alloy 1-ANN has a yield strength of 610 MPa (88.5 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 58% of cobalt-chrome alloy grades. Elongation at break is 35% and the elastic modulus is 230 GPa (33.4 Msi).
Thermal6
F1537 Alloy 1-ANN 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 12.3 µm/m·K (6.83 µin/in·°F).
Electrical3
F1537 Alloy 1-ANN conducts electricity at 1.9 % IACS, worse than 52% 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 F1537 Alloy 1-ANN takes about 210 MJ of energy and emits 14 kg of CO₂ — more than 80% of cobalt-chrome alloy grades. Typical recycled content is 20%.
Manufacturability8
F1537 Alloy 1-ANN's machinability is not recommended (14/100, better than 71% of cobalt-chrome alloy grades); weldability good (55/100); formability fair (35/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with F1537 Alloy 1-ANN
Is F1537 Alloy 1 easy to machine?
Very difficult: rigid setups, sharp positive-rake carbide or ceramic tools, low speed / heavy feed and flood coolant to avoid work-hardened glaze; grinding and EDM are common for finish features.
Can F1537 Alloy 1 be welded?
Low carbon content makes it the most weldable F1537 alloy — GTAW or laser/electron-beam with matching filler, clean argon shielding, low heat input; post-weld solution anneal restores ductility.
Can F1537 Alloy 1 be formed, bent or molded?
Cold formability is poor due to the very high work-hardening rate; forge or upset hot (≈1050–1180 °C) or warm work below recrystallisation to raise strength, with intermediate anneals.
What surface finishes work on F1537 Alloy 1?
Not anodizable; electropolish, passivate per ASTM F86, and mirror-polish bearing surfaces (Ra < 0.05 µm); porous or HA coatings can be applied for bone ingrowth.
F1537 Alloy 1 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 | 26 – 30 | 28 |
| Mo | 5 – 7 | 6 |
| Ni | ≤ 1 | 0.3 |
| Fe | ≤ 0.75 | 0.3 |
| CAlloy 1 = low carbon | ≤ 0.14 | 0.05 |
| Si | ≤ 1 | 0.5 |
| Mn | ≤ 1 | 0.5 |
| N | ≤ 0.25 | 0.15 |
| Cobalance, nominally ~62–64 % | balance | — |
F1537 Alloy 1-ANN — frequently asked
What is F1537 Alloy 1-ANN used for?
F1537 Alloy 1-ANN is typically used for hip and knee implant components, trauma fixation devices, bone plates and screws, spinal rods and connectors, modular implant connectors and dental frameworks. In short: most weldable F1537 alloy; highest ductility Co-Cr-Mo; low-carbon implant grade.
What is the yield strength of F1537 Alloy 1-ANN?
F1537 Alloy 1-ANN has a typical yield strength of 610 MPa (88.5 ksi) and a tensile strength of 1,000 MPa (145 ksi) — stronger than 58% of cobalt-chrome alloy grades. Strength varies by condition: see the 3 listed tempers.
Is F1537 Alloy 1-ANN easy to machine?
Not especially — machinability is rated not recommended (14/100, better than 71% of cobalt-chrome alloy grades). Very difficult: rigid setups, sharp positive-rake carbide or ceramic tools, low speed / heavy feed and flood coolant to avoid work-hardened glaze; grinding and EDM are common for finish features.
Can F1537 Alloy 1-ANN be welded?
Yes — weldability is rated good (55/100). Low carbon content makes it the most weldable F1537 alloy — GTAW or laser/electron-beam with matching filler, clean argon shielding, low heat input; post-weld solution anneal restores ductility.
What surface finishes work on F1537 Alloy 1-ANN?
Not anodizable; electropolish, passivate per ASTM F86, and mirror-polish bearing surfaces (Ra < 0.05 µm); porous or HA coatings can be applied for bone ingrowth.
Can F1537 Alloy 1-ANN be formed, bent or molded?
Cold formability is poor due to the very high work-hardening rate; forge or upset hot (≈1050–1180 °C) or warm work below recrystallisation to raise strength, with intermediate anneals.
What is the maximum service temperature of F1537 Alloy 1-ANN?
F1537 Alloy 1-ANN 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 F1537 Alloy 1-ANN and F1537 Alloy 1-WW?
ANN is the default condition — most commonly stocked raw bar condition: maximum ductility for subsequent forging, machining or forming of implant components. WW: highest-strength condition of Alloy 1 — pick for slender, highly loaded implants (femoral stems, spinal rods) where fatigue strength governs. Yield strength is 610 MPa in ANN versus 1,050 MPa in WW.
Sources
- ASTM F1537 — Standard Specification for Wrought Cobalt-28Chromium-6Molybdenum Alloys for Surgical Implants (UNS R31537, R31538, R31539) — ASTM International (2020)
- ISO 5832-12 — Implants for surgery, metallic materials, Part 12: Wrought cobalt-chromium-molybdenum alloy — ISO (2019)
- ASM Handbook Vol.23 — Materials for Medical Devices — ASM International (2012)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials — ASM International (1990)
- Medical-grade Co-28Cr-6Mo bar datasheets (Carpenter, Sandvik, VDM) — various 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.