🔍 Inconel 625 vs Inconel 718 – Comparison Table
| Property / Feature | Inconel 625 | Inconel 718 |
|---|---|---|
| Main Strength Mechanism | Solid solution strengthening | Precipitation hardening (γ'' and γ') |
| Typical Applications | Chemical processing, marine, aerospace, heat exchangers | Jet engines, gas turbines, high-stress parts |
| Composition Highlights | High Mo (8–10%) and Nb (3–4%) | High Nb (4.75–5.5%) and Mo (2.8–3.3%) |
| Tensile Strength | ~827 MPa (120 ksi) | Up to 1,300–1,500 MPa (190–220 ksi) |
| Yield Strength | ~414 MPa (60 ksi) | Up to 1,000–1,200 MPa (145–175 ksi) |
| Hardness (Annealed) | ~200 HB | Up to 330–440 HB (after aging) |
| Service Temp. Range | -253 °C to 982 °C (-423 °F to 1,800 °F) | -252 °C to 704 °C (-422 °F to 1,300 °F) |
| Corrosion Resistance | Excellent (chlorides, seawater, oxidizing and reducing acids) | Very good (less resistant than 625 to some acids) |
| Weldability | Excellent – no post-weld heat treatment needed | Good – but requires post-weld aging for full strength |
| Creep Resistance | Good, but less than 718 | Excellent |
| Machinability | Fair | More difficult (due to hardening) |
| Density | 8.44 g/cm³ | 8.19 g/cm³ |
| Cost | Generally more expensive | More affordable for strength-per-cost |
✅ Summary
Use Inconel 625 for superior corrosion resistance, especially in chemical, marine, and high-temperature oxidation environments.
Use Inconel 718 when high strength at intermediate temperatures and excellent fatigue/corrosion resistance are needed - ideal for aerospace and turbine applications.
