MP35N in Space Exploration: Why Engineers Use It
Quick answer: MP35N (UNS R30035) is a nickel-cobalt-chromium-molybdenum alloy that reaches 260–300 ksi (1,790–2,070 MPa) tensile strength after cold drawing and aging, stays tough down to cryogenic temperatures and resists stress-corrosion cracking and hydrogen embrittlement. That is why space and aerospace engineers use it for critical fasteners, springs, cables and small high-load parts. It is not a hot-section alloy – its service limit is about 315 °C (600 °F).
Need bar stock? See MP35N bars – AMS 5844 / 5845.
What is MP35N?
MP35N is a “multiphase” alloy of roughly 35% nickel, 35% cobalt, 20% chromium and 10% molybdenum. Cold working creates a very fine second phase in its structure, and a low-temperature aging treatment (about 540–595 °C) raises its strength further. The result is one of the strongest corrosion-resistant alloys available, while it stays ductile, tough and non-magnetic. It contains almost no iron, so it is not a stainless steel.
Why MP35N Suits Space Hardware
| Property | MP35N (cold drawn + aged) | Why it matters in space |
|---|---|---|
| Strength | 260–300 ksi tensile, 230+ ksi yield | Smaller, lighter fasteners and springs for the same load – every gram counts at launch |
| Cryogenic behaviour | Strength and elongation rise as temperature falls; no embrittlement | Safe near liquid-oxygen and liquid-hydrogen systems and in cold orbital environments |
| Stress-corrosion cracking | NASA testing found no SCC after 180 days in 3.5% salt water | Launch sites are coastal; hardware sits in salt air for months before flight |
| Hydrogen embrittlement | Highly resistant | Important for parts near hydrogen propellant and for highly loaded bolts |
| Fatigue and toughness | Retains ductility at very high strength | Survives launch vibration and repeated load cycles |
| Magnetism | Non-magnetic | No interference with sensitive instruments and magnetometers |
Where MP35N Is Used in Space and Aerospace
- High-strength fasteners: bolts and studs for structures and mechanisms where a 260 ksi+ bolt saves weight and space. See also MP35N in aircraft fasteners.
- Springs and cables: deployment, latch and release-mechanism springs and wire, where high strength and corrosion resistance must last for years without maintenance.
- Cryogenic propellant hardware: small high-load parts, pins and fasteners near liquid-oxygen and liquid-hydrogen systems.
- Actuator and landing-gear parts: pins, shafts and bushings in aircraft and landers that need strength, toughness and corrosion resistance together.
Where MP35N Is Not Used
MP35N is limited to about 315 °C (600 °F). It is not used for turbine blades, combustion chambers, rocket nozzles or re-entry heat shields. Those parts need true high-temperature alloys:
| Hot-section need | Typical material |
|---|---|
| Engine parts and high-temperature bolting up to about 650 °C | Inconel 718 or A286 |
| Rocket nozzle extensions and thrusters (around 1,200 °C+, coated) | C103 niobium alloy |
For a detailed side-by-side, read MP35N vs Inconel 718.
MP35N Specifications for Aerospace
| Specification | Condition | Typical tensile strength |
|---|---|---|
| AMS 5758 | Solution treated | ≈ 130 ksi (900 MPa) |
| AMS 5844 | Solution treated + cold drawn | ≈ 255 ksi (1,760 MPa) |
| AMS 5845 | Cold drawn + aged | 260–300 ksi (1,790–2,070 MPa) |
Other designations: UNS R30035, NACE MR0175 / ISO 15156 (sour service), ASTM F562 (medical). Values are typical and depend on bar size and cold work – guaranteed minimums are on the mill certificate.
MP35N Chemical Composition (UNS R30035)
| Element | Weight % |
|---|---|
| Nickel (Ni) | 33.0 – 37.0 |
| Cobalt (Co) | Balance (≈ 35) |
| Chromium (Cr) | 19.0 – 21.0 |
| Molybdenum (Mo) | 9.0 – 10.5 |
| Titanium (Ti) | 1.0 max |
| Iron (Fe) | 1.0 max |
| Manganese (Mn) | 0.15 max |
| Silicon (Si) | 0.15 max |
| Carbon (C) | 0.025 max |
| Phosphorus (P) | 0.015 max |
| Sulphur (S) | 0.010 max |
| Boron (B) | 0.015 max |
Buying MP35N Bar for Aerospace Projects
ASC LLP, Mumbai, supplies MP35N round bar, hex bar and rod to AMS 5758, AMS 5844 and AMS 5845, with EN 10204 3.1 certificates, full heat traceability, cut-to-length pieces for prototypes, and PMI, hardness or third-party inspection on request. For other high-strength bar grades see 35NCD16, CoCrMo and titanium bars.
Frequently Asked Questions
Is MP35N used in spacecraft?
Yes. MP35N is used in launch vehicles, satellites and other space hardware mainly for high-strength fasteners, springs, cables and small structural or mechanism parts where very high strength, toughness at cryogenic temperatures and resistance to stress-corrosion cracking are needed in a small, light section.
What temperature can MP35N handle?
MP35N keeps its properties from cryogenic temperatures up to about 315 °C (600 °F). Above that it loses strength, so it is not used for turbine blades, combustion chambers or re-entry heat shields; alloys such as Inconel 718 or C103 niobium are used there.
Why is MP35N good at cryogenic temperatures?
Its tensile strength, yield strength and elongation all increase as temperature falls, and it does not become brittle. This makes it suitable for fasteners and parts near liquid-oxygen and liquid-hydrogen systems.
MP35N or Inconel 718 – which is better for aerospace?
MP35N is stronger (260–300 ksi vs about 180–200 ksi tensile) and more resistant to stress-corrosion cracking and hydrogen embrittlement, so it is chosen for critical fasteners and springs below about 315 °C. Inconel 718 is the better choice for hot parts up to about 650 °C.
Which specifications cover aerospace MP35N bar?
MP35N (UNS R30035) bar for aerospace is supplied to AMS 5758 (solution treated), AMS 5844 (solution treated and cold drawn) and AMS 5845 (cold drawn and aged), with EN 10204 3.1 mill test certificates.
Related Reading
- MP35N bars – AMS 5844, AMS 5845 and AMS 5758
- MP35N vs Inconel 718 – which alloy suits your needs?
- How MP35N ensures safety in aircraft fasteners
- MP35N in oil, gas and marine industries
Need MP35N for a space or aerospace project? Send your grade, specification, size and quantity to marketing@amardeepsteel-centre.com or call 022-67439130.
