Cobalt-Chrome Alloy F1537 Alloy 3-HW (Hot Worked)
Heat-treated state · default condition
ASTM F1537 Alloy 3 · UNS R31539
Standard mill supply for forged implant components — balanced strength, ductility and machinability.
Values for the HW condition
Other F1537 Alloy 3 tempers and conditions
F1537 Alloy 3 is listed in 3 conditions; see the grade overview at F1537 Alloy 3.
Compare all 3 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Annealed | Softest condition — choose for subsequent forging, deep machining or when maximum ductility is needed. | 600 | 1,000 | 32 | 28 HRC | — |
HWDefaultThis page Hot Worked | Standard mill supply for forged implant components — balanced strength, ductility and machinability. | 930 | 1,280 | 20 | 36 HRC | — |
Warm Worked | Highest strength and fatigue life — chosen for machined-from-bar hip stems and other high-cycle load-bearing parts. | 1,300 | 1,550 | 18 | 45 HRC | — |
What is F1537 Alloy 3-HW?
F1537 Alloy 3-HW is F1537 Alloy 3 heat treated to HW — standard mill supply for forged implant components — balanced strength, ductility and machinability. F1537 Alloy 3-HW has a yield strength of 930 MPa (135 ksi) and a tensile strength of 1,280 MPa (186 ksi) — stronger than 81% of cobalt-chrome alloy grades. Elongation at break is 20% and the elastic modulus is 230 GPa (33.4 Msi). F1537 Alloy 3-HW 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 — 90/100, better than 95% of cobalt-chrome alloy grades
- Polishes to a fine finish — 92/100, better than 93% of cobalt-chrome alloy grades
- Tough — resists crack growth — 70 MPa·√m (63.7 ksi·√in), better than 82% of cobalt-chrome alloy grades
- Forms and bends easily — 25/100, better than 82% of cobalt-chrome alloy grades
- High strength — 930 MPa (135 ksi), better than 81% of cobalt-chrome alloy grades
Limitations
- Limited service temperature — 500°C (932 °F), worse than 87% of cobalt-chrome alloy grades
F1537 Alloy 3-HW properties
Typical room-temperature values for F1537 Alloy 3-HW; 17 are specific to this condition. Other listed values are F1537 Alloy 3 reference data and may not represent this condition. Bars are the position among cobalt-chrome alloy grades.
Physical3
F1537 Alloy 3-HW 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).
Mechanical14
F1537 Alloy 3-HW has a yield strength of 930 MPa (135 ksi) and a tensile strength of 1,280 MPa (186 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
F1537 Alloy 3-HW is rated for continuous service to 500°C (932 °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 3-HW conducts electricity at 2 % IACS, better than 79% of cobalt-chrome alloy grades.
Chemical & Environmental3
Corrosion resistance is excellent (90/100), better than 95% of cobalt-chrome alloy grades.
Sustainability4
Producing a kilogram of F1537 Alloy 3-HW takes about 170 MJ of energy and emits 12 kg of CO₂ — more than 63% of cobalt-chrome alloy grades. Typical recycled content is 20%.
Manufacturability7
F1537 Alloy 3-HW's machinability is not recommended (12/100, better than 61% of cobalt-chrome alloy grades); weldability poor (30/100); formability poor (25/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with F1537 Alloy 3-HW
Is F1537 Alloy 3 easy to machine?
Very difficult: use rigid setups, sharp coated carbide or ceramic inserts, low speed / heavy positive feed and flood coolant to avoid the severe work-hardened skin; grinding and EDM are common alternatives.
Can F1537 Alloy 3 be welded?
Not recommended for load-bearing joints — high carbon promotes carbide precipitation and hot cracking; if unavoidable use low-heat-input laser or electron-beam welding with matched filler and post-weld solution anneal.
Can F1537 Alloy 3 be formed, bent or molded?
Shape by hot forging (≈1100–1180 °C) or warm working; cold forming is impractical because of the extremely high work-hardening rate.
What surface finishes work on F1537 Alloy 3?
Not anodizable — finish by grinding, mirror polishing of bearing surfaces (Ra < 0.02 µm), electropolishing, then passivation per ASTM F86; porous coatings applied by plasma spray or sintered beads.
F1537 Alloy 3 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 |
| Chigh-carbon type, forms M23C6 carbides | 0.15 – 0.35 | 0.25 |
| Larare-earth addition producing the dispersed oxide phase | 0.03 – 0.14 | 0.08 |
| Ni | ≤ 1 | — |
| Fe | ≤ 0.75 | — |
| Si | ≤ 1 | — |
| Mn | ≤ 1 | — |
| N | ≤ 0.25 | — |
| Co | balance | — |
F1537 Alloy 3-HW — frequently asked
What is F1537 Alloy 3-HW used for?
F1537 Alloy 3-HW is typically used for orthopedic implant stems, joint replacement components, knee femoral components, modular hip necks and tapers, spinal rods and connectors and trauma fixation hardware. In short: dispersion-strengthened implant grade; improved implant fatigue strength; very low machinability rating.
What is the yield strength of F1537 Alloy 3-HW?
F1537 Alloy 3-HW has a typical yield strength of 930 MPa (135 ksi) and a tensile strength of 1,280 MPa (186 ksi) — stronger than 81% of cobalt-chrome alloy grades. Strength varies by condition: see the 3 listed tempers.
Is F1537 Alloy 3-HW 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, sharp coated carbide or ceramic inserts, low speed / heavy positive feed and flood coolant to avoid the severe work-hardened skin; grinding and EDM are common alternatives.
Can F1537 Alloy 3-HW be welded?
Not readily — weldability is rated poor (30/100). Not recommended for load-bearing joints — high carbon promotes carbide precipitation and hot cracking; if unavoidable use low-heat-input laser or electron-beam welding with matched filler and post-weld solution anneal.
What surface finishes work on F1537 Alloy 3-HW?
Not anodizable — finish by grinding, mirror polishing of bearing surfaces (Ra < 0.02 µm), electropolishing, then passivation per ASTM F86; porous coatings applied by plasma spray or sintered beads.
Can F1537 Alloy 3-HW be formed, bent or molded?
Shape by hot forging (≈1100–1180 °C) or warm working; cold forming is impractical because of the extremely high work-hardening rate.
What is the maximum service temperature of F1537 Alloy 3-HW?
F1537 Alloy 3-HW is rated for continuous use to about 500°C (932 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between F1537 Alloy 3-HW and F1537 Alloy 3-WW?
HW is the default condition — standard mill supply for forged implant components — balanced strength, ductility and machinability. WW: highest strength and fatigue life — chosen for machined-from-bar hip stems and other high-cycle load-bearing parts. Yield strength is 930 MPa in HW versus 1,300 MPa in WW.
Sources
- ASTM F1537 Standard Specification for Wrought Cobalt-28Chromium-6Molybdenum Alloys for Surgical Implants (UNS R31537, R31538, R31539) — ASTM International (2020)
- ASTM F86 Standard Practice for Surface Preparation and Marking of Metallic Surgical Implants — ASTM International (2021)
- ASM Handbook Vol.23: Materials for Medical Devices — ASM International (2012)
- ASM Handbook Vol.2: Properties and Selection — Nonferrous Alloys and Special-Purpose Materials (Cobalt alloys) — ASM International (1990)
- Wrought Co-28Cr-6Mo medical bar datasheets (Carpenter/Sandvik/Villares type) — various mills (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.