MP159®

1. Ultra-high strength: Through multiple mechanisms including cold deformation-induced ε-phase strengthening and aging precipitation strengthening, its tensile strength at room temperature can reach 1790–2070 MPa, placing it among the first-tier commercial high-strength alloys currently available.
2. Excellent high-temperature strength retention: It maintains a tensile strength of no less than 1000 MPa at 650°C, with superior creep strength, far outperforming ordinary stainless steels and traditional nickel-based alloys.
3. Superior corrosion resistance: It exhibits excellent resistance to stress corrosion cracking in chloride media, as well as resistance to seawater, salt spray, H₂S, and corrosion from various acids and alkalis.
4. Good stress relaxation resistance: Highly suitable for manufacturing fasteners that need to maintain high preload at high temperatures.
5. Excellent fatigue resistance: Its high-cycle fatigue strength exceeds 700 MPa (at 10⁷ cycles), effectively extending the service life of aerospace fasteners under alternating loads.
6. Conforms to standards: It meets relevant standards such as UNS R30159, AMS 5841, AMS 5842, and AMS 5843.

MP159® follows a special strengthening path of 'solution treatment + cold drawing + aging':
1. Solution Annealing: Heat to 1065°C ± 5°C, hold for 4-8 hours, then water cool (must be rapid cooling to prevent carbide precipitation along grain boundaries), resulting in a fully austenitic microstructure and eliminating prior processing hardening.
2. Cold Drawing Deformation: Perform cold drawing deformation of 48% ± 1% at room temperature (cold working reduction can reach over 60%). This induces martensitic transformation and establishes stored deformation energy. Controlling the deformation amount is critical: below 30% results in weak subsequent aging strengthening, while above 60% may cause longitudinal splitting.
3. Aging Hardening: Heat to 650–675°C, hold for 4–12 hours, then air cool. Precipitation of ε phase and γ' phase (Ni₃X type) occurs, which pin dislocations to achieve strengthening.
Important Notes:
1. This alloy is a multiphase strengthened cobalt-based alloy. High strength cannot be obtained through heat treatment alone; it must undergo synergistic cold deformation and aging.
2. All mechanical processing (turning, milling, drilling, tapping, etc.) must be completed in the solution-treated state, followed by aging treatment to achieve final properties.
3. The aging temperature must not exceed 680°C, as this would cause the ε phase to revert back to the γ phase, resulting in a sharp drop in strength.
4. Weldability is generally poor, and it is typically not recommended for welded structures.

1. Continuous Operating Temperature (balancing strength and oxidation resistance): Recommended ≤ 650°C. Below this temperature, it maintains microstructural stability and excellent mechanical properties.
2. Short-Term Exposure Temperature: Can reach approximately 700°C, but strength and oxidation resistance will significantly decrease.
3. Typical Application Temperature: The design operating temperature for high-temperature fasteners in aircraft engines usually ranges from 500–650°C.
4. Low-Temperature Use: The alloy exhibits good performance across a wide temperature range from -253°C to 650°C.

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