Cobalt-Chrome Alloy MP159 CW+A
Precip hard · default condition
UNS R30159
CW+A = cold worked (~45–50%) and aged
Standard high-strength condition for bolts, studs and springs rated ≥1930 MPa UTS to 590 °C.
Values for the CW+A condition
Other MP159 tempers and conditions
MP159 is listed in 5 conditions; see the grade overview at MP159.
Compare all 5 conditionsHide
| Condition · open for datasheet | Best for | Yield MPa | Tensile MPa | Elong. % | Hardness | Conductivity |
|---|---|---|---|---|---|---|
Solution annealed | Choose for cold heading, wire drawing, deep forming or machining before the strengthening sequence. | 450 | 950 | 55 | 22 HRC | — |
Solution annealed then aged | Used for forgings and thick sections where the required cold work cannot be imparted; strength well below CW+A. | 900 | 1,310 | 20 | 40 HRC | 1.8 % IACS |
Cold worked | Intermediate stock condition for wire/bar that will be aged after forming or coiling. | 1,520 | 1,650 | 12 | 46 HRC | 1.6 % IACS |
CW+ADefaultThis page Cold worked (~45–50%) and aged | Standard high-strength condition for bolts, studs and springs rated ≥1930 MPa UTS to 590 °C. | 1,830 | 1,965 | 10 | 52 HRC | — |
CW+A | Fine-wire product form for high-stress, non-magnetic, corrosion-resistant springs and diaphragms. | 1,900 | 2,070 | 6 | 54 HRC | 1.7 % IACS |
What is MP159 CW+A?
MP159 CW+A is MP159 in the CW+A condition — standard high-strength condition for bolts, studs and springs rated ≥1930 MPa UTS to 590 °C. MP159 CW+A has a yield strength of 1,830 MPa (265 ksi) and a tensile strength of 1,965 MPa (285 ksi) — stronger than 92% of cobalt-chrome alloy grades. Elongation at break is 10% and the elastic modulus is 200 GPa (29 Msi). MP159 CW+A has a density of 8.3 g/cm³ (0.3 lb/in³), lighter than 80% of cobalt-chrome alloy grades. It melts at 1,315°C (2,399 °F).
Advantages
- High strength — 1,830 MPa (265 ksi), better than 92% of cobalt-chrome alloy grades
- Tough — resists crack growth — 70 MPa·√m (63.7 ksi·√in), better than 82% of cobalt-chrome alloy grades
- Low embodied carbon — 10.5 kg CO₂/kg, better than 77% of cobalt-chrome alloy grades
Limitations
- Difficult to weld — 20/100, worse than 87% of cobalt-chrome alloy grades
- Poor heat conductor — 11.5 W/m·K (6.64 BTU/hr·ft·°F), worse than 86% of cobalt-chrome alloy grades
- Limited service temperature — 593°C (1,099 °F), worse than 82% of cobalt-chrome alloy grades
MP159 CW+A properties
Typical room-temperature values for MP159 CW+A; 12 are specific to this condition. Other listed values are MP159 reference data and may not represent this condition. Bars are the position among cobalt-chrome alloy grades.
Physical3
MP159 CW+A has a density of 8.3 g/cm³ (0.3 lb/in³), lighter than 80% of cobalt-chrome alloy grades. It melts at 1,315°C (2,399 °F).
Mechanical14
MP159 CW+A has a yield strength of 1,830 MPa (265 ksi) and a tensile strength of 1,965 MPa (285 ksi) — stronger than 92% of cobalt-chrome alloy grades. Elongation at break is 10% and the elastic modulus is 200 GPa (29 Msi).
Thermal5
MP159 CW+A is rated for continuous service to 593°C (1,099 °F). It conducts heat at 11.5 W/m·K (6.64 BTU/hr·ft·°F), worse than 86% of cobalt-chrome alloy grades. Thermal expansion is 12.8 µm/m·K (7.11 µin/in·°F).
Electrical3
MP159 CW+A conducts electricity at 1.7 % IACS, worse than 92% of cobalt-chrome alloy grades.
Chemical & Environmental3
Corrosion resistance is very good (80/100), better than 63% of cobalt-chrome alloy grades.
Sustainability4
Producing a kilogram of MP159 CW+A takes about 145 MJ of energy and emits 10.5 kg of CO₂ — less than 73% of cobalt-chrome alloy grades. Typical recycled content is 20%.
Manufacturability7
MP159 CW+A's machinability is not recommended (10/100, better than 52% of cobalt-chrome alloy grades); weldability poor (20/100); formability not recommended (5/100).
Common Calculations5
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with MP159 CW+A
Is MP159 easy to machine?
Extremely gummy and work-hardening: use rigid setups, positive-rake carbide or ceramic at low speed (5–15 m/min in aged condition), heavy constant feed, flood high-pressure coolant, and avoid dwelling; rough machine in the annealed state whenever possible.
Can MP159 be welded?
Fusion welding is discouraged for load-bearing joints because it dissolves the cold-work/γ′ strengthening; if required use GTAW/EBW with matching or Ni-base filler and re-solution + re-age (strength will still fall short of CW+A).
Can MP159 be formed, bent or molded?
Cold head, draw or coil only in the solution-annealed or partially cold-worked condition with high-pressure lubricants and frequent interstage anneals; age after forming — aged material has almost no cold ductility.
What surface finishes work on MP159?
Naturally passive and needs no coating; threads are usually silver-plated, dry-film lubricated or cetyl-alcohol coated to prevent galling, and surfaces can be electropolished or passivated per ASTM A967.
MP159 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 |
|---|---|---|
| Ni | 25 – 26 | 25.5 |
| Cr | 18.5 – 19.5 | 19 |
| Fe | 8.5 – 9.5 | 9 |
| Mo | 6.75 – 7.25 | 7 |
| Tiprincipal γ′ former | 2.75 – 3.25 | 3 |
| Nbreported as Cb | 0.4 – 0.7 | 0.6 |
| Al | 0.1 – 0.3 | 0.2 |
| C | ≤ 0.04 | 0.02 |
| Si | ≤ 0.15 | — |
| Mn | ≤ 0.15 | — |
| S | ≤ 0.01 | — |
| P | ≤ 0.02 | — |
| Cobalance, nominally ~36% | balance | — |
MP159 CW+A — frequently asked
What is MP159 CW+A used for?
MP159 CW+A is typically used for aerospace springs, high-strength fasteners, landing gear components and surgical instruments. In short: higher strength than MP35N; 1830 MPa yield fastener alloy; very poor machinability.
What is the yield strength of MP159 CW+A?
MP159 CW+A has a typical yield strength of 1,830 MPa (265 ksi) and a tensile strength of 1,965 MPa (285 ksi) — stronger than 92% of cobalt-chrome alloy grades. Strength varies by condition: see the 5 listed tempers.
Is MP159 CW+A easy to machine?
Not especially — machinability is rated not recommended (10/100, better than 52% of cobalt-chrome alloy grades). Extremely gummy and work-hardening: use rigid setups, positive-rake carbide or ceramic at low speed (5–15 m/min in aged condition), heavy constant feed, flood high-pressure coolant, and avoid dwelling; rough machine in the annealed state whenever possible.
Can MP159 CW+A be welded?
Not readily — weldability is rated poor (20/100). Fusion welding is discouraged for load-bearing joints because it dissolves the cold-work/γ′ strengthening; if required use GTAW/EBW with matching or Ni-base filler and re-solution + re-age (strength will still fall short of CW+A).
What surface finishes work on MP159 CW+A?
Naturally passive and needs no coating; threads are usually silver-plated, dry-film lubricated or cetyl-alcohol coated to prevent galling, and surfaces can be electropolished or passivated per ASTM A967.
Can MP159 CW+A be formed, bent or molded?
Cold head, draw or coil only in the solution-annealed or partially cold-worked condition with high-pressure lubricants and frequent interstage anneals; age after forming — aged material has almost no cold ductility.
What is the maximum service temperature of MP159 CW+A?
MP159 CW+A is rated for continuous use to about 593°C (1,099 °F). Strength falls off well before that limit — check the elevated-temperature data for load-bearing parts.
What is the difference between MP159 CW+A and MP159-SA?
CW+A is the default condition — standard high-strength condition for bolts, studs and springs rated ≥1930 MPa UTS to 590 °C. SA: choose for cold heading, wire drawing, deep forming or machining before the strengthening sequence. Yield strength is 1,830 MPa in CW+A versus 450 MPa in SA.
Sources
- AMS 5842 — Alloy Bars, Forgings and Rings, 36Co-25Ni-19Cr-9Fe-7Mo-3Ti, Work Strengthened and Aged — SAE International (2017)
- MP159 Alloy (UNS R30159) technical data — Specialty/aerospace alloy producers (SPS Technologies, Latrobe Specialty Metals) (2020)
- ASM Handbook Vol.2 — Properties and Selection: Nonferrous Alloys and Special-Purpose Materials (cobalt alloys) — ASM International (1990)
- MMPDS-style typical mechanical property data for multiphase Co-Ni fastener alloys — Battelle/FAA (2021)
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.