Hangbo Alloy Group
Shanghai · Est. 2012
UNS R30159 / W.Nr. 2.4601 — Multiphase-strengthened Co-Ni-Cr alloy delivering 1800 MPa tensile strength, biocompatibility, and exceptional performance in medical, aerospace, and oil & gas applications.
MP159 (UNS R30159 / W.Nr. 2.4601) is a multiphase, precipitation-hardenable cobalt-nickel-chromium superalloy developed by Latrobe Steel (now Carpenter Technology) as an advanced evolution of the well-known MP35N alloy. The addition of titanium (2.5–3.25%) and niobium (0.25–0.75%) to the MP35N base composition creates a sophisticated triple-strengthening system that combines work hardening, gamma-prime (Ni3(Al,Ti)) precipitation, and the unique multiphase (HCP/FCC) transformation that gives this alloy family its name. In the cold-worked plus aged condition, MP159 achieves tensile strength exceeding 1800 MPa (260 ksi) — among the highest strengths available in a corrosion-resistant biomedical and aerospace alloy.
The defining feature of MP159 is its “multiphase” strengthening mechanism. Upon cold working, the FCC (face-centered cubic) austenitic matrix partially transforms to HCP (hexagonal close-packed) platelets through a strain-induced martensitic-like transformation. When subsequently aged, gamma-prime precipitates form on the HCP platelets, creating an exceptionally stable, high-strength microstructure. This combination allows MP159 to retain useful strength at temperatures up to 600°C (1110°F), well beyond the practical limit of MP35N (~400°C), making it the preferred choice for high-temperature fasteners, springs, and engine components.
Beyond its impressive mechanical properties, MP159 offers excellent corrosion resistance in seawater, chloride environments, and many chemical media, combined with full biocompatibility per ASTM F562 and ISO 5832-6. This unique combination of properties has made MP159 the alloy of choice for orthopedic bone screws, spinal fixation hardware, dental implants, missile and rocket motor casings, and high-strength non-magnetic components for naval and oilfield applications. Hangbo Alloy Group supplies MP159 in bar, wire, plate, and custom forging forms in both annealed and cold-worked + aged conditions.
The chemistry of MP159 builds on the MP35N foundation (Co-Ni-Cr-Mo) with strategically added titanium, niobium, and iron. Titanium is the primary gamma-prime (Ni3Ti) former; niobium contributes to both gamma-prime and gamma double-prime strengthening, and the higher iron content (8–10% vs ≤1% in MP35N) provides economic benefits and aids in deoxidation during VIM melting. Carbon and nitrogen are kept very low to prevent carbide and nitride formation that would reduce the alloy's ductility and corrosion resistance.
| Element | Min % | Max % |
|---|---|---|
| Cobalt (Co) | 35.5 | 37.0 |
| Nickel (Ni) | 25.5 | 27.0 |
| Chromium (Cr) | 18.0 | 20.0 |
| Molybdenum (Mo) | 6.5 | 7.5 |
| Iron (Fe) | 8.0 | 10.0 |
| Titanium (Ti) | 2.5 | 3.25 |
| Aluminum (Al) | 0.05 | 0.30 |
| Niobium (Nb) | 0.25 | 0.75 |
| Carbon (C) | — | 0.02 |
| Manganese (Mn) | — | 0.20 |
| Silicon (Si) | — | 0.20 |
| Phosphorus (P) | — | 0.015 |
| Sulfur (S) | — | 0.010 |
| Boron (B) | — | 0.030 |
| Nitrogen (N) | — | 0.02 |
MP159 has an FCC austenitic matrix in the annealed condition, which partially transforms to HCP martensite during cold work. This dual-phase structure contributes to its exceptional work-hardening response. The alloy is non-magnetic in the annealed condition (permeability <1.005) and remains essentially non-magnetic even after cold work and aging, which is a critical requirement for non-magnetic downhole tools and certain naval applications. Density of 8.32 g/cm³ is similar to cobalt-chromium alloys (typically 8.3–8.5 g/cm³) and is suitable for medical implants where radiographic visibility is required.
| Property | Value | Unit |
|---|---|---|
| Density | 8.32 | g/cm3 |
| Melting Range | 1310 - 1400 | °C |
| Specific Heat (21°C) | 420 | J/kg·K |
| Thermal Conductivity (21°C) | 13.0 | W/m·K |
| Electrical Resistivity (21°C) | 1.05 | μΩ·m |
| Modulus of Elasticity (21°C) | 200 | GPa |
| Mean CTE (21-93°C) | 12.5 | μm/m·°C |
| Magnetic Permeability | <1.005 | Non-magnetic |
MP159 exhibits a remarkable range of mechanical properties depending on the thermomechanical condition. In the annealed condition, it has moderate strength (~830 MPa tensile) and excellent ductility (~50% elongation) suitable for cold heading and forming. After 40–50% cold work plus aging at 480–650°C, tensile strength reaches 1820 MPa (264 ksi) with yield strength of 1725 MPa (250 ksi) — approaching the strength of maraging steels while maintaining full corrosion resistance. Values below represent the cold-worked + aged condition per AMS 5842.
| Property | Annealed (AMS 5843) | Cold Worked + Aged (AMS 5842) |
|---|---|---|
| Tensile Strength | 830 MPa (120 ksi) | 1820 MPa (264 ksi) |
| Yield Strength (0.2% offset) | 415 MPa (60 ksi) | 1725 MPa (250 ksi) |
| Elongation in 4D | 50% | 10% |
| Reduction of Area | 65% | 35% |
| Hardness | 30 HRC max | 45 - 53 HRC |
| Charpy V-notch Impact | >150 J | 20 - 30 J |
MP159 is unique among high-strength alloys in that its peak properties require a carefully controlled combination of cold work and aging. The recommended process route for high-strength applications is:
For wire and small-diameter bar, warm working at 700–800°C with 40–50% reduction is also used, followed by direct aging. This route avoids the need for intermediate anneals in long production sequences. Over-aging above 700°C leads to gradual strength loss and is not recommended for high-strength applications.
MP159 retains useful strength at elevated temperatures significantly better than its predecessor MP35N. In the cold-worked + aged condition, the alloy maintains approximately 70% of its room-temperature tensile strength at 500°C and 50% at 600°C. This makes it the highest-strength biocompatible or non-magnetic alloy available for service above 400°C. Stress-rupture life at 540°C and 1380 MPa exceeds 100 hours, suitable for high-temperature fastener and spring applications.
| Temperature (°C) | Tensile Strength (MPa) | Yield Strength (MPa) | Elongation (%) |
|---|---|---|---|
| 21 (Room) | 1820 | 1725 | 10 |
| 316 | 1700 | 1580 | 11 |
| 427 | 1600 | 1480 | 12 |
| 482 | 1500 | 1380 | 13 |
| 538 | 1380 | 1240 | 14 |
| 593 | 1240 | 1100 | 15 |
| 649 | 1030 | 900 | 18 |
| 704 | 760 | 650 | 22 |
MP159 inherits the excellent corrosion resistance of the MP35N family — including resistance to seawater, chlorides, hydrogen sulfide, sulfuric acid, and most organic media — while adding high-temperature strength. The high chromium content (18–20%) forms a passive chromium oxide film that protects against pitting and crevice corrosion in marine and industrial environments. The molybdenum addition (6.5–7.5%) enhances resistance to reducing acids and chloride pitting.
MP159 occupies a unique niche as a high-strength, corrosion-resistant, biocompatible, and non-magnetic superalloy. Its combination of properties makes it the material of choice in the following demanding applications:
Hangbo Alloy Group manufactures and supplies MP159 in the full range of mill forms required by medical, aerospace, and oilfield customers. All material is supplied with full material test reports, heat treatment certification, and, for medical grades, biocompatibility documentation per ASTM F562 or ISO 5832-6.
| Standard | Description |
|---|---|
| ASTM F562 | Wrought Cobalt-Nickel-Chromium-Molybdenum Alloy Bar and Wire for Surgical Implants |
| ISO 5832-6 | Implants for Surgery — Wrought Cobalt-Nickel-Chromium-Molybdenum Alloy |
| AMS 5841 | Alloy Bar and Wire, High-Strength, Cold Worked and Aged |
| AMS 5842 | Alloy Bar and Wire, Annealed |
| AMS 5843 | Alloy Bar and Wire, Solution Annealed |
| ASME SB-562 | Boiler and Pressure Vessel Code |
| NACE MR0175 / ISO 15156 | Sour Gas Service (no hardness limit) |
MP159 has a density of 8.32 g/cm³ (0.301 lb/in³) at room temperature, similar to MP35N (8.43 g/cm³) and other cobalt-nickel multiphase superalloys. The high density is due to its substantial cobalt, nickel, and chromium content.
The melting range of MP159 is approximately 1310–1400°C (2390–2550°F). The relatively high melting point reflects the alloy's high cobalt and nickel content combined with chromium and molybdenum additions.
MP159 (UNS R30159) nominal composition: Co 35.5–37.0%, Ni 25.5–27.0%, Cr 18.0–20.0%, Mo 6.5–7.5%, Fe 8.0–10.0%, Ti 2.5–3.25%, Al 0.05–0.30%, Nb 0.25–0.75%, C ≤0.02%, Mn ≤0.20%, Si ≤0.20%, S ≤0.010%, P ≤0.015%, B ≤0.030%, N ≤0.02%.
Key standards for MP159 include ASTM F562 (medical bar and wire), AMS 5841 (bar and wire for medical implants), AMS 5842 (high-strength bar and wire), AMS 5843 (annealed condition), and ASME SB-562 for pressure vessel applications. The alloy is also covered by ISO 5832-6 for surgical implants.
MP159 is supplied in three primary conditions: (1) Annealed at 1175–1200°C for 4–8 hours followed by water quench, providing a workable hardness of ~145 HB. (2) Cold worked + aged (recommended for high strength): solution anneal, cold work 30–50%, then age at 480–650°C for 4 hours. (3) Warm worked + aged for wire and bar: 40–50% reduction at 700–800°C then aged 480–650°C for 4 hours.
MP159 is a higher-strength, more thermally stable evolution of MP35N. Key differences: MP159 adds titanium (2.5–3.25%) and niobium (0.25–0.75%) for gamma-prime strengthening, plus higher iron (8–10% vs ≤1% in MP35N) and slightly more chromium. MP159 achieves higher tensile strength (1800+ MPa vs 1800 MPa for cold-worked MP35N) and retains strength to higher temperatures (up to 600°C vs 400°C for MP35N). It is also more economical due to higher iron content.
MP159 is a premium superalloy with high cobalt and nickel content. Rough price range: $60–95/kg for round bar in standard sizes, with cold-worked + aged condition commanding 20–30% premium over annealed. Wire and small-diameter bar are at the higher end. Medical-grade material (ASTM F562) carries additional certification costs. Contact Hangbo Alloy Group for current pricing.
MP159 is available as round bars (3–200 mm dia), wires (0.5–10 mm), plates (0.5–25 mm), and small forgings. Cold-worked and aged bar/wire is the most common form for high-strength applications. Hangbo Alloy Group supplies MP159 per ASTM F562, AMS 5841/5842/5843, and ISO 5832-6 specifications.
MP159 has limited weldability in the aged condition due to its high strength and potential for heat-affected zone (HAZ) softening. It is best welded in the annealed condition using GTAW or laser welding with matching filler metal, then re-aged. Electron beam and plasma welding are preferred to minimize HAZ. For most medical and aerospace applications, the alloy is machined from bar rather than welded.
MP159 can be used at temperatures up to approximately 600°C (1110°F) in the cold-worked + aged condition, with rapid strength loss above 650°C. For optimum stress-rupture performance, the alloy is typically limited to 540°C (1000°F) for long-term service. The annealed condition has lower maximum service temperature (~400°C). MP159 retains non-magnetic behavior at cryogenic temperatures down to -196°C.
MP159 is used in high-strength, high-reliability applications including: (1) Medical implants — orthopedic bone screws, spinal fixation devices, dental implants, surgical instruments. (2) Aerospace — fasteners, springs, turbine engine components, missile parts. (3) Oil & gas — downhole tools, high-strength non-magnetic components for directional drilling. (4) Chemical processing — pump shafts, valve stems, mixer blades. (5) Marine — non-magnetic structural components for naval applications.
Yes, MP159 (per ASTM F562 and ISO 5832-6) is biocompatible and widely used for medical implants. The alloy forms a passive chromium oxide layer that resists corrosion in body fluids. However, it contains nickel (~26%), which is a known allergen for some patients, so titanium or cobalt-chromium alternatives are preferred for nickel-sensitive patients. Long-term clinical data shows excellent biocompatibility for spinal, orthopedic, and dental applications.
Hangbo Alloy Group supplies MP159 in bar, wire, plate, and custom forging forms in both annealed and cold-worked + aged conditions. We support medical-grade certifications per ASTM F562 and ISO 5832-6, aerospace specifications per AMS 5841/5842/5843, and oilfield NACE MR0175 compliance with full traceability documentation.
For quotations, material certifications, or technical consultation, contact our sales team or call +86-136-1165-6360. We typically respond within 10 minutes.
Request a quotation for MP159 round bars, wire, plates, or custom forgings in annealed or cold-worked + aged conditions. We supply medical-grade (ASTM F562), aerospace (AMS 5841/5842/5843), and NACE MR0175 compliant material with full certification.