Cobalt-Chrome Alloy MP159: Properties, Tempers & Uses

MP159 tempers and conditions

MP159 is supplied in 5 conditions, soft to hard. CW+A is the default FabDigit quotes; the values on this page are for it.

Compare all 5 conditionsHide

Condition · open for datasheet	Best for	Yield MPa	Tensile MPa	Elong. %	Hardness	Conductivity
SA Solution annealed	Choose for cold heading, wire drawing, deep forming or machining before the strengthening sequence.	450	950	55	22 HRC	—
SA+A 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
CW 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-SPRING 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?

MP159 is a multiphase, precipitation-hardenable Co-Ni-Cr-Mo alloy with Ti and Al additions (UNS R30159), strengthened by combined cold work and aging, and related to MP35N but capable of higher strength. In the cold-worked and aged condition it reaches 1830 MPa yield, 1965 MPa tensile, 10% elongation and about 52 HRC, with service to 593 °C; it is supplied mainly as wire, bar and fastener or spring stock. Machinability (score 10), weldability (20) and formability (5) are all poor, so MP35N is the usual choice when slightly lower strength buys easier processing. MP159 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). MP159 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).

What is MP159 used for?

aerospace springs
high-strength fasteners
landing gear components
surgical instruments

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 properties

Typical room-temperature values for MP159-CW+A; bars are the position among cobalt-chrome alloy grades.

Physical3

MP159 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).

Density8.3 g/cm³0.3 lb/in³

Melting Point (Solidus)1,315°C2,399 °F

Liquidus Temperature1,400°C2,552 °F

Mechanical14

MP159 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).

Elastic (Young's) Modulus200 GPa29 Msi

Shear Modulus77 GPa11.2 Msi

Bulk Modulus170 GPa24.7 Msi

Poisson's Ratio0.3

Tensile Strength (Ultimate)1,965 MPa285 ksi

Yield Strength (0.2% offset)1,830 MPa265 ksi

Elongation at Break10%

Reduction in Area38%

Compressive Strength1,900 MPa276 ksi

Shear Strength1,150 MPa167 ksi

Fatigue Strength (Endurance Limit)760 MPa110 ksi

Fracture Toughness (K_IC)70 MPa·√m63.7 ksi·√in

Hardness, Rockwell C52 HRC

Hardness, Vickers560 HV

Thermal5

MP159 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).

Thermal Conductivity11.5 W/m·K6.6 BTU/hr·ft·°F

Specific Heat Capacity420 J/kg·K0.1 BTU/lb·°F

Thermal Expansion (CTE, 20–100 °C)12.8 µm/m·K7.1 µin/in·°F

Max Service Temperature (continuous)593°C1,099 °F

Min Service Temperature-253°C-423 °F

Electrical3

MP159 conducts electricity at 1.7 % IACS, worse than 92% of cobalt-chrome alloy grades.

Electrical Conductivity1.7 % IACS

Electrical Resistivity1.02×10⁻⁶ Ω·m40.2 µΩ·in

Magnetic Responsenon-magnetic

Chemical & Environmental3

Corrosion resistance is very good (80/100), better than 63% of cobalt-chrome alloy grades.

Galvanic Potential (seawater, vs SCE)-0.2 V

Corrosion ResistanceVery good80/100

Chemical Resistance SummaryHighly resistant to chloride pitting/crevice attack, seawater and sour (H₂S) environments; excellent resistance to chloride SCC and hydrogen embrittlement; attacked by hot concentrated reducing acids (HCl, HF) and molten salts.

Sustainability4

Producing a kilogram of MP159 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%.

Embodied Energy (primary production)145 MJ/kg62,339 BTU/lb

Embodied Carbon (primary production)10.5 kg CO₂/kg

Embodied Water320 L/kg38.3 gal/lb

Typical Recycled Content20%

Manufacturability7

MP159's machinability is not recommended (10/100, better than 52% of cobalt-chrome alloy grades); weldability poor (20/100); formability not recommended (5/100).

MachinabilityNot recommended10/100

Machinability Rating (AISI 1212 = 100 %)8%

WeldabilityPoor20/100

Formability (cold)Not recommended5/100

Brazeability / SolderabilityFair40/100

PolishabilityVery good82/100

Anodizing Responsen/a — cobalt-base alloy; use passivation or dry-film lubricant/silver plating on threads instead

Common Calculations5

Specific Strength (UTS / density)calculated237 kN·m/kg

Specific Stiffness (E / density)calculated24.1 MN·m/kg

Modulus of Resiliencecalculated8,372 kJ/m³

Thermal Diffusivitycalculated3.3 mm²/s

Thermal Shock Resistance Indexcalculated9

Values are nominal handbook figures for design screening. Certified mill or lot data ships with every FabDigit order on request.

Strength versus weight in the cobalt-chrome alloy family

Yield strength against density for every cobalt-chrome alloy grade FabDigit runs. MP159 is highlighted; hover a dot for its name, or open the interactive family chart.

Working with MP159

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.

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

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.

Equivalent designations

Standards and trade names that resolve to Cobalt-Chrome Alloy MP159 in FabDigit's catalog. Equivalence is nominal — check the exact specification when certification matters.

UNS: R30159

Other High-temperature Co-Cr-W cobalt-chrome alloy grades

Closest cobalt-chrome alloy grades by properties

Compare MP159 with…

Benchmark MP159 against the top 3 neighbours

How much does MP159 cost?

MP159 is a high-cost cobalt-chrome alloy ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.

MP159 — frequently asked

What is MP159 used for?

MP159 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?

MP159 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 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 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?

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 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?

MP159 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.

How much does MP159 cost?

MP159 is a high-cost cobalt-chrome alloy ($$$$), pricier than about 78% of the materials FabDigit quotes. Part price depends far more on geometry, tolerance and quantity than on the raw stock — upload a CAD file for a live quote.

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)