What are MP35N Fasteners? The Ultimate Guide to High-Strength, Corrosion-Resistant Fasteners
MP35N fasteners are premium-grade bolts, screws, nuts, and studs manufactured from the cobalt-nickel-chromium-molybdenum superalloy known as MP35N. This alloy, pioneered by SPS Technologies (now part of Precision Castparts Corp.), is specifically engineered to deliver an unparalleled combination of ultra-high strength, exceptional corrosion resistance, and excellent fatigue performance. MP35N fasteners are the material of choice for the most demanding, mission-critical applications where failure is not an option, outperforming common stainless steel and nickel-based superalloys.
Key Characteristics and Properties of MP35N Alloy Fasteners
The superior performance of MP35N fasteners stems from a unique multiphase strengthening process (cold working and aging). Their defining characteristics include:
Ultra-High Strength: MP35N fasteners achieve an ultimate tensile strength typically ranging from 260 to 300 ksi (1,790 - 2,070 MPa), far exceeding standard high-strength steel fasteners like Grade 8 or even Inconel 718.
Exceptional Corrosion Resistance: They exhibit outstanding resistance to a wide range of corrosive media, making them ideal for harsh environments. This includes superior resistance to saltwater corrosion, sour gas (H2S), and chloride-induced stress corrosion cracking (SCC).
Excellent Fatigue Strength: The alloy's microstructure provides superior resistance to failure under cyclic loading and vibration, ensuring long-term reliability and durability in dynamic applications.
High-Temperature Performance: These fasteners retain a significant portion of their mechanical properties at elevated temperatures, performing reliably up to approximately 800°F (427°C).
Biocompatibility: MP35N is compliant with ASTM F562, making it a premier material for medical implant fasteners such as bone screws and orthopedic devices.
MP35N Chemical Composition and Mechanical Properties
MP35N Chemical Composition (Nominal %):
MP35N Typical Mechanical Properties (for Fasteners):
Ultimate Tensile Strength: 260 - 300 ksi (1,790 - 2,070 MPa)
Yield Strength (0.2% Offset): 225 - 260 ksi (1,550 - 1,790 MPa)
Elongation: 10% (typical)
Reduction of Area: 40% (typical)
Hardness: 36 - 46 HRC
Main Application Fields for MP35N Fasteners
MP35N fasteners are specified in industries where extreme reliability is paramount:
Aerospace & Defense: Used in critical aircraft engine components, airframe structures, and landing gear systems where the highest strength-to-weight ratio and resistance to fatigue are required.
Oil & Gas Industry: Essential for downhole tools in HPHT (High-Pressure High-Temperature) wells and sour service applications. They provide reliable performance in environments with H2S, CO2, and high chloride content.
Medical Device Manufacturing: A primary choice for orthopedic implants, surgical fasteners, bone screws, and spinal fixation devices due to their biocompatibility, high strength, and resistance to bodily fluids.
Marine and Chemical Processing: Used in offshore platforms, subsea equipment, and chemical plants where components are exposed to highly corrosive saltwater and chemical environments.
MP35N fasteners are cobalt alloy fasteners and ultra-high strength fasteners known for their exceptional corrosion resistance and resistance to stress corrosion cracking. They are critical aerospace fasteners and oil & gas fasteners for HPHT well and sour service applications. As biocompatible fasteners, they are also leading medical implant fasteners and orthopedic fasteners. When comparing MP35N vs Inconel 718 or MP35N vs A-286, MP35N offers superior fatigue strength and tensile strength, making it the ideal solution for mission-critical fasteners in the most demanding environments.
