MP35N vs Inconel 718: Which Alloy Suits Your Needs?
Quick answer: Choose MP35N when you need the highest strength (260–300 ksi) and the best resistance to seawater, sour gas, stress-corrosion cracking and hydrogen embrittlement at temperatures below about 315 °C (600 °F). Choose Inconel 718 when the part runs hot – up to about 650–700 °C (1,200–1,300 °F) – or must be welded, at lower cost.
Need material? See MP35N bars (AMS 5844 / 5845) and Inconel 718 round bars.
MP35N vs Inconel 718 – Comparison Table
| Property | MP35N (UNS R30035) | Inconel 718 (UNS N07718) |
|---|---|---|
| Alloy type | Ni-Co-Cr-Mo “multiphase” alloy | Ni-Cr-Fe-Nb precipitation-hardening superalloy |
| How it is strengthened | Cold work + low-temperature aging | Solution treatment + two-step aging (γ″ precipitates) |
| Tensile strength (typical) | 260 – 300 ksi (1,790 – 2,070 MPa), AMS 5845 | ≈ 180 – 185 ksi (1,240 – 1,280 MPa), aged AMS 5662/5663 |
| Yield strength (typical) | ≈ 230 – 280 ksi | ≈ 150 ksi (1,035 MPa) |
| Maximum useful temperature | ≈ 315 °C (600 °F) | ≈ 650 – 700 °C (1,200 – 1,300 °F) |
| Cryogenic service | Excellent – strength rises at low temperature | Excellent – used down to −253 °C |
| Corrosion / SCC / H₂ embrittlement | Outstanding in seawater, chlorides and H₂S | Good; not its main selection reason |
| NACE MR0175 / ISO 15156 | Yes | Yes (also API 6A718) |
| Weldability | Weldable, but the weld zone loses cold-work strength | Very good – resists strain-age cracking |
| Machinability | Difficult – work-hardens rapidly | Difficult – machine in solution-annealed condition |
| Density | 8.43 g/cm³ | 8.19 g/cm³ |
| Magnetic | No | No |
| Relative cost | Higher (≈ 35% cobalt) | Lower |
| Main specifications | AMS 5758, AMS 5844, AMS 5845, ASTM F562, ISO 5832-6 | AMS 5662, AMS 5663, ASTM B637, API 6A718 |
Chemical Composition – MP35N vs Inconel 718 (wt %)
| Element | MP35N | Inconel 718 |
|---|---|---|
| Nickel (Ni) | 33.0 – 37.0 | 50.0 – 55.0 |
| Cobalt (Co) | Balance (≈ 35) | 1.0 max |
| Chromium (Cr) | 19.0 – 21.0 | 17.0 – 21.0 |
| Molybdenum (Mo) | 9.0 – 10.5 | 2.80 – 3.30 |
| Niobium + Tantalum (Nb+Ta) | – | 4.75 – 5.50 |
| Titanium (Ti) | 1.0 max | 0.65 – 1.15 |
| Aluminium (Al) | – | 0.20 – 0.80 |
| Iron (Fe) | 1.0 max | Balance (≈ 18) |
| Carbon (C) | 0.025 max | 0.08 max |
What Is MP35N?
MP35N is a nickel-cobalt-chromium-molybdenum alloy of roughly 35% Ni, 35% Co, 20% Cr and 10% Mo. Cold drawing followed by a low-temperature aging treatment gives it one of the highest strengths of any corrosion-resistant alloy, while it stays tough, non-magnetic and resistant to stress-corrosion cracking. It is supplied to AMS 5758, AMS 5844 and AMS 5845 for aerospace, ASTM F562 / ISO 5832-6 for medical devices, and NACE MR0175 for sour service. More: MP35N bars.
What Is Inconel 718?
Inconel 718 (UNS N07718) is a nickel-chromium-iron superalloy strengthened by niobium-rich precipitates formed during a two-step aging treatment. It keeps high strength, fatigue and creep resistance up to about 650–700 °C, is readily welded, and is the most widely used superalloy in jet engines, gas turbines and high-temperature bolting. More: Inconel 718 round bars.
Which Alloy Should You Choose?
Choose MP35N if:
- You need the highest possible strength in a small section – critical fasteners, springs, cables or shafts.
- The part sees seawater, chlorides or sour gas, or must resist stress-corrosion cracking and hydrogen embrittlement.
- Service temperature stays below about 315 °C, or the part works at cryogenic temperatures.
- You need a medical-grade alloy (ASTM F562) – for example pacemaker leads and guidewires.
Choose Inconel 718 if:
- The part runs hot – turbine discs, casings, exhaust parts or high-temperature bolting up to about 650–700 °C.
- The part must be welded or fabricated.
- You need high strength and fatigue resistance at a lower cost than MP35N.
- You are making oil-tool components to API 6A718.
Typical Applications
| Industry | MP35N | Inconel 718 |
|---|---|---|
| Aerospace | High-strength fasteners, springs, cables, landing-gear and actuator parts | Engine discs, shafts, casings, high-temperature fasteners |
| Oil & gas | Downhole tools, wireline, subsea fasteners, sour-service springs | Wellhead and downhole components (API 6A718), hangers, valves |
| Medical | Pacemaker leads, guidewires, orthopaedic parts | Rarely used |
| Power generation | – | Gas-turbine components, high-temperature bolting |
| Marine | Seawater shafts, fasteners and springs | Less common |
Frequently Asked Questions
Is MP35N stronger than Inconel 718?
Yes. Cold-drawn and aged MP35N (AMS 5845) reaches about 260–300 ksi (1,790–2,070 MPa) tensile strength, compared with about 180–185 ksi (1,240–1,280 MPa) for aged Inconel 718 bar to AMS 5662/5663.
Which alloy is better at high temperature?
Inconel 718. It keeps useful strength up to about 650–700 °C (1,200–1,300 °F), while MP35N is limited to about 315 °C (600 °F).
Which has better corrosion resistance?
MP35N. It has outstanding resistance to seawater, chlorides, sour (H₂S) environments, stress-corrosion cracking and hydrogen embrittlement. Inconel 718 has good corrosion resistance but is chosen mainly for high-temperature strength.
Are both MP35N and Inconel 718 NACE MR0175 approved?
Yes. Both are listed in NACE MR0175 / ISO 15156 for sour oil and gas service, within the hardness and condition limits given in the standard. Inconel 718 is also covered by API 6A718.
Which is easier to weld and machine?
Inconel 718 is easier to weld – it resists strain-age cracking and can be aged after welding. Both are hard to machine; MP35N work-hardens very quickly and is best machined before aging.
Which alloy costs more?
MP35N is usually more expensive than Inconel 718 because it contains about 35% cobalt and needs heavy cold working to reach its strength.
Buy MP35N and Inconel 718 Bars from ASC LLP
ASC LLP (Amardeep Steel Centre LLP), Mumbai, supplies MP35N round bar, hex bar and rod to AMS 5844 / AMS 5845 / NACE MR0175 and Inconel 718 bars to AMS 5662 / AMS 5663 / ASTM B637, plus Inconel 718 fasteners and alternatives such as A286. All material comes with EN 10204 3.1 certificates; cut pieces and third-party inspection on request. Send your requirement to sales@amardeepsteel.com or call 022-67439130.
Related reading: MP35N in space exploration · MP35N aircraft fasteners · Inconel 718 in aerospace and power generation
Inconel® is a registered trademark of the Special Metals Corporation group of companies. MP35N® is a registered trademark of SPS Technologies, LLC.
