Inconel 625

Key Features:

  1. Inconel 625 prevents attack in alkalis, marine & fresh water and natural salts
  2. Resistance to oxidizing and non-oxidizing media
  3. Prevents pitting & crevice corrosion and SCC
  4. High temperature scaling resistance
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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 

  1. Corrosion Resistance

   – Outstanding resistance to seawater, acids (HCl, H₂SO₄), and chlorides. 

   – Resists pitting, crevice corrosion, and stress-corrosion cracking (SCC). 

  1. High-Temperature Performance

   – Retains strength up to 980°C (1,800°F). 

   – Excellent oxidation resistance (forms protective Cr₂O₃ layer). 

  1. Mechanical Properties

   – Tensile Strength: 830–1030 MPa (~120–150 ksi) 

   – Yield Strength: 410–550 MPa (~60–80 ksi) 

   – Elongation: 30–50% (high ductility) 

  1. 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. 

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