Inconel 718

Key Features:

  1. Inconel 718 is extremely resistant to chlorine & sulfur based stress corrosion cracking
  2. High temperature & aqueous corrosion resistance
  3. High mechanical strength
  4. Superior welding properties
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About Inconel 718

Inconel 718 is a nickel-chromium-based superalloy strengthened by niobium (Nb) and molybdenum (Mo), making it one of the most widely used high-performance alloys in aerospace, oil & gas, and nuclear industries. It is known for its excellent strength, creep resistance, and corrosion resistance at high temperatures (up to 700°C / 1300°F). It is available in the form of Wire, Bar/rod, Strip/tape.

Inconel 718 Industrial Nomenclatures: UNS N07718, Nicrofer 5219, Alvac 718, Haynes 718, Altemp 718, Nickel 718, IN718, AFNOR NC 19 Fe Nb, AWS 013

Key Properties of Inconel 718 

Element Percentage Role
Nickel (Ni) 50-55% Base metal, provides corrosion resistance
Chromium (Cr) 17-21% Enhances oxidation resistance
Iron (Fe) Balance (~18%) Lowers cost, stabilizes structure
Niobium (Nb) 4.75-5.5% Forms γ” (gamma double prime) precipitates for strengthening
Molybdenum (Mo) 2.8-3.3% Improves creep resistance
Titanium (Ti) 0.65-1.15% Forms γ’ (gamma prime) precipitates
Aluminum (Al) 0.2-0.8% Strengthening via precipitation
Carbon (C) ≤ 0.08% Affects weldability & hardness

Key Characteristics

✔ High Strength – Maintains mechanical properties up to 700°C (1300°F). 

✔ Excellent Fatigue & Creep Resistance – Ideal for cyclic loading applications. 

✔ Good Corrosion Resistance – Resists oxidation, pitting, and chloride stress corrosion. 

✔ Weldability – Unlike many superalloys, Inconel 718 is readily weldable without post-weld cracking (due to slow γ” precipitation). 

✔ Fabricability – Can be machined, forged, and formed, though it requires specialized techniques. 

 Applications of Inconel 718 

  1. Aerospace & Jet Engines

– Turbine blades, disks, and shafts (due to high strength-to-weight ratio) 

– Rocket motor casings, afterburners 

– Aircraft structural components 

  1. Oil & Gas Industry

– Downhole drilling tools 

– Valves, pumps, and wellhead components (resists sour gas environments) 

  1. Nuclear & Power Generation

– Nuclear reactor core components 

– Heat exchangers, turbine seals 

  1. Automotive & Racing

– Turbocharger rotors, exhaust valves 

 Comparison with Other Superalloys 

Property Inconel 718 Inconel 625 Inconel 617 Hastelloy X
Primary Strengthening γ” (Ni₃Nb) Solid solution Solid solution & carbides Solid solution
Max Temp (°C) 700 980 1000 1200
Weldability Excellent Good Moderate Good
Key Applications Jet engines, turbines Chemical processing Nuclear reactors Combustors

 Advantages & Limitations 

 ✔ Advantages 

– High strength-to-weight ratio 

– Good weldability compared to other superalloys 

– Resists oxidation & corrosion in harsh environments 

 ✖ Limitations 

– Expensive (due to high Ni, Nb content) 

– Difficult to machine (requires specialized tools) 

– Limited to ~700°C (higher temps require alloys like Inconel 617/625) 

Conclusion 

Inconel 718 is a versatile, high-strength superalloy widely used in aerospace, oil & gas, and nuclear industries due to its exceptional mechanical properties, weldability, and corrosion resistance. While it is costly and challenging to machine, its performance in extreme conditions makes it indispensable. 

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