MP35N®

1. Ultra-high strength: Achieving a tensile strength of 1790–2070 MPa at room temperature through cold deformation-induced martensitic transformation and aging precipitation strengthening, placing it among the first-tier commercial high-strength alloys currently available.
2. Excellent corrosion resistance: Possesses outstanding resistance to stress corrosion cracking in chloride media, as well as resistance to seawater, salt spray, H₂S, and corrosion from various acids and alkalis.
3. Non-magnetic: With extremely low relative permeability (< 1.001), suitable for applications in precision instruments, aerospace, and medical implants.
4. Good biocompatibility: Exhibits excellent corrosion resistance in the human body's fluid environment, making it widely used in orthopedic and dental implants.
5. Superior fatigue resistance: High-cycle fatigue strength exceeds 700 MPa (at 10⁷ cycles), effectively extending the service life of fasteners under alternating loads.
6. Compliance with standards: Conforms to relevant standards such as UNS R30035, AMS 5844, AMS 5845, and ISO 5832-6 (Cobalt-Nickel-Chromium-Molybdenum Alloys for Surgical Implants).

MP35N® 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 precipitation of harmful phases), resulting in a fully austenitic microstructure and eliminating prior processing work 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: less than 30% results in weak subsequent aging strengthening, while more than 60% may cause longitudinal splitting.
3. Aging Hardening: Heat to 600–650°C, hold for 4–12 hours, then air cool. Precipitation of γ' phase (Ni₃X type) occurs, which pin dislocations to achieve strengthening.
Important Notes:
1. This alloy is a ultra-high-strength cobalt-based alloy. High strength cannot be achieved through heat treatment alone; it must be obtained through the synergistic effect of cold deformation and aging.
2. All machining operations (turning, milling, drilling, tapping, etc.) must be completed in the solution-treated state, followed by aging treatment to achieve the final properties.
3. The aging temperature must not exceed 700°C, as exceeding this will cause over-aging of the microstructure and result in reduced strength.
4. Weldability is generally poor, and it is typically not recommended for welded structures.

1. Continuous operating temperature (balancing strength and corrosion resistance): It is recommended to be ≤ 400°C. Below this temperature, the microstructure stability and excellent mechanical properties can be maintained.
2. Short-term exposure temperature: It can reach up to approximately 600°C, but the strength and corrosion resistance will significantly decrease.
3. Typical application temperature: The design operating temperature of aerospace fasteners usually ranges from 300 to 400°C.
4. Low-temperature use: This alloy exhibits good performance over a wide temperature range from -253°C to 400°C, with no magnetism and excellent toughness retained.

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