Inconel 625
Key Features:
- Inconel 625 prevents attack in alkalis, marine & fresh water and natural salts
- Resistance to oxidizing and non-oxidizing media
- Prevents pitting & crevice corrosion and SCC
- High temperature scaling resistance
About Inconel 625
Inconel 625 is a nickel-chromium-molybdenum superalloy renowned for its exceptional corrosion resistance, high strength, and excellent fabricability. It performs well in extreme environments, including seawater, acidic conditions, and high temperatures. It is available in the form of Wires, Bars, Strips/Tapes.
Inconel 625 Industrial Nomenclatures: Inconel 625, Chornin 625, Altemp 625, Nickelvac 625, Haynes 625, Nicrofer 6020, W.Nr 2.4856, AWS 012,UNS N06625
Composition (Nominal %)
Element | Percentage | Role |
Nickel (Ni) | 58% min | Provides corrosion resistance & high-temp stability |
Chromium (Cr) | 20–23% | Enhances oxidation & corrosion resistance |
Molybdenum (Mo) | 8–10% | Improves pitting/crevice corrosion resistance |
Niobium (Nb) | 3.15–4.15% | Strengthens via solid-solution hardening |
Iron (Fe) | ≤ 5% | Balances cost & properties |
Carbon (C) | ≤ 0.10% | Minimizes carbide precipitation |
Key Properties
- Corrosion Resistance
– Outstanding resistance to seawater, acids (HCl, H₂SO₄), and chlorides.
– Resists pitting, crevice corrosion, and stress-corrosion cracking (SCC).
- High-Temperature Performance
– Retains strength up to 980°C (1,800°F).
– Excellent oxidation resistance (forms protective Cr₂O₃ layer).
- Mechanical Properties
– Tensile Strength: 830–1030 MPa (~120–150 ksi)
– Yield Strength: 410–550 MPa (~60–80 ksi)
– Elongation: 30–50% (high ductility)
- Fabrication & Weldability
– Easier to machine than most superalloys (but still work-hardens).
– Highly weldable (TIG, MIG, laser, electron beam).
Applications
🌊 Marine & Offshore
– Subsea components (valves, fasteners)
– Propeller blades & seawater piping
⚗️ Chemical Processing
– Acid production equipment
– Reactors & heat exchangers
🛢️ Oil & Gas
– Downhole & wellhead components
– Flare stacks in sour gas environments
Comparison with Similar Alloys
Property | Inconel 625 | Inconel 718 | Hastelloy C-276 |
Max Temp. | 980°C | 700°C | 1090°C |
Corrosion Resistance | Excellent (Cr + Mo) | Good | Best (Higher Mo) |
Strength | High (solution-hardened) | Higher (age-hardened) | Moderate |
Cost | $$$ | $$ | $$$$ |
Best for:
– Extreme corrosion (better than 718, cheaper than C-276).
– High-strength + weldability (no age-hardening needed).
Limitations:
– Not as strong as age-hardenable alloys (e.g., 718).
– Lower temp limit than Inconel 601.
Machining & Welding Tips
🔧 Machining
– Tooling: Use carbide or ceramic tools with sharp edges.
– Speeds: Low-to-medium RPM, high feed rates.
– Coolant: Essential to prevent work hardening.
⚡ Welding
– Best Methods: TIG (most common), MIG, laser.
– Filler Metal: ERNiCrMo-3 (matches base metal).
– Post-Weld Heat Treatment (PWHT): Rarely needed (low risk of sensitization).
📌 Conclusion
Inconel 625 is a top choice for corrosive, high-stress environments where weldability and fabricability matter. It outperforms 316 stainless steel and Inconel 600 in harsh chemical settings but is less strong than 718 in high-load aerospace applications.