Cobalt-Chrome Alloy MP159-SA (Solution annealed)
Heat-treated state
UNS R30159
Choose for cold heading, wire drawing, deep forming or machining before the strengthening sequence.
Values for the SA 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 |
|---|---|---|---|---|---|---|
SAThis page 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+ADefault 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-SA?
MP159-SA is MP159 heat treated to SA — choose for cold heading, wire drawing, deep forming or machining before the strengthening sequence. MP159-SA has a yield strength of 450 MPa (65.3 ksi) and a tensile strength of 950 MPa (138 ksi) — weaker than 96% of cobalt-chrome alloy grades. Elongation at break is 55% and the elastic modulus is 200 GPa (29 Msi). MP159-SA 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). CW+A is the default condition FabDigit quotes; SA is available on request or by drawing note.
Advantages
- Forms and bends easily — 65/100, better than 100% of cobalt-chrome alloy grades
- Ductile — tolerates forming and impact — 55%, better than 96% 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
- Low strength — 450 MPa (65.3 ksi), worse than 96% 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
MP159-SA properties
Typical room-temperature values for MP159-SA; 11 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-SA 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-SA has a yield strength of 450 MPa (65.3 ksi) and a tensile strength of 950 MPa (138 ksi) — weaker than 96% of cobalt-chrome alloy grades. Elongation at break is 55% and the elastic modulus is 200 GPa (29 Msi).
Thermal5
MP159-SA is rated for continuous service to 650°C (1,202 °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-SA 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-SA 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-SA's machinability is poor (18/100, better than 91% of cobalt-chrome alloy grades); weldability fair (45/100); formability good (65/100).
Values are nominal handbook figures for design screening. Confirm any required mill or lot documentation when quoting.
Working with MP159-SA
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-SA — frequently asked
What is MP159-SA used for?
MP159-SA 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-SA?
MP159-SA has a typical yield strength of 450 MPa (65.3 ksi) and a tensile strength of 950 MPa (138 ksi) — weaker than 96% of cobalt-chrome alloy grades. Strength varies by condition: see the 5 listed tempers.
Is MP159-SA easy to machine?
Not especially — machinability is rated poor (18/100, better than 91% 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-SA be welded?
With care — weldability is rated fair (45/100). 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-SA?
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-SA 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-SA?
MP159-SA is rated for continuous use to about 650°C (1,202 °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.