SPS-M-646 - MP35N Aerospace Fasteners
SPS-M-646 is the spec from SPS Technologies describing the use of MP35N, which is a high-strength corrosion-resistant cobalt-nickel-chromium-molybdenum alloy. MP35N is widely specified within the aerospace industry, the medical field, the offshore industry, and the oil & gas industry due to its exceptional combination of properties: high tensile strength, toughness, ductility, and corrosion resistance.
Yet MP35N is able to maintain excellent corrosion resistance in harsh environments such as seawater, chlorides, sweet gases, and sour gases when yield strengths rise above 200 KSI (1380 MPa). It is the strongest alloy approved within the NACE MR0175 spec for sour service environments without restriction and is the first choice for critical aerospace and other industrial components.
Properties of MP35N per SPS-M-646
MP35N derives its exceptional standing from a complex combination of chemical, manufacturing, and processing characteristics. Its strength lies in:
– Chemical composition: 35% Cobalt, 35% Nickel, 20% Chromium, 10% Molybdenum
– Melt processing: clean to the core through vacuum induction melting (VIM) and vacuum arc remelting (VAR)
– Cold working/aging: achieves exceptionally high strength values > 260 ksi / > 1793 MPa while retaining ductility with 40% reduction in area
– Annealed properties: approximately 150 ksi ultimate tensile strength, about 60 ksi yield strength, approximately 68% elongation, and about 75% reduction in area
In relation to stainless steels and other nickel alloys, like 718, MP35N has higher strength with equal or better corrosion resistance in many applications. Its non-magnetic and biocompatibility properties also open it up to additional applications.
Applications of SPS-M-646 MP35N
- Structural components on the Space Shuttle
- Airframes and tie rods
- Petrochemical and marine equipment
- Submersibles and leading-edge strips
- Any application demanding extreme strength and corrosion resistance
MP35N SPECIFICATIONS
MP35N HEAT TREATING CONDITIONS
Standards specifying thermal processing and quality verification for MP35N.
Certified Material for Critical Service
MP35N is widely certified for critical service applications, ensuring reliability in aerospace, medical, oil & gas, and high-performance industrial environments. All supplied MP35N products come with full traceability and certification, including:
- Chemical Composition Certificates: Confirming cobalt, nickel, chromium, and molybdenum content per AMS and SPS specifications.
- Mechanical Test Reports: Tensile strength, hardness, and elongation verified according to AMS 5844, AMS 5758, and SPS-M-646.
- Non-Destructive Testing (NDT): Ultrasonic and visual inspections per AMS-STD-2154 to ensure defect-free material.
- Heat Treatment Certification: Verification of precipitation hardening and work strengthening procedures.
This ensures MP35N meets the highest standards for critical, high-stress, and corrosion-prone applications, making it suitable for mission-critical aerospace components, surgical implants, and offshore equipment.