Excellent Corrosion Resistance of Inconel 625
Inconel 625 is a solid-solution-strengthened nickel-chromium-molybdenum-niobium alloy known for its exceptional corrosion resistance—especially in chloride-containing, oxidizing acid, and seawater environments. It also provides excellent high-temperature oxidation resistance and thermal strength, making it widely used in chemical processing, aerospace, and marine engineering.
What is Inconel 625?
Inconel 625 (UNS N06625) is a high-performance nickel-based alloy composed primarily of nickel, with additions of chromium, molybdenum, and niobium. It is strengthened by solid solution hardening, has excellent mechanical properties, and outstanding resistance to a variety of corrosive media. Inconel 625 is highly weldable and formable and can be used from cryogenic temperatures up to around 980°C.
Inconel 625 Equivalent Grades
| Standard System | Equivalent Grade |
| UNS | N06625 |
| W.Nr. | 2.4856 |
| ASTM | B443 / B446 / B564 |
| DIN | NiCr22Mo9Nb |
| ISO / EN | NiCr22Mo9Nb |
Inconel 625 Chemical Composition (Typical)
| Element | Content (%) |
| Nickel (Ni) | ≥ 58.0 |
| Chromium (Cr) | 20.0 – 23.0 |
| Molybdenum (Mo) | 8.0 – 10.0 |
| Niobium (Nb) | 3.15 – 4.15 |
| Iron (Fe) | ≤ 5.0 |
| Manganese (Mn) | ≤ 0.50 |
| Silicon (Si) | ≤ 0.50 |
| Carbon (C) | ≤ 0.10 |
| Phosphorus (P) | ≤ 0.015 |
| Sulfur (S) | ≤ 0.015 |
| Aluminum (Al) | ≤ 0.40 |
| Titanium (Ti) | ≤ 0.40 |
Inconel 625 Mechanical Properties (Annealed, Room Temperature)
| Property | Typical Value |
| Tensile Strength | ≥ 827 MPa |
| Yield Strength (0.2%) | ≥ 414 MPa |
| Elongation | ≥ 30% |
| Brinell Hardness | ~200 HB |
Inconel 625 Physical Properties
| Property | Value |
| Density | 8.44 g/cm³ |
| Melting Point | 1290–1350°C |
| Thermal Conductivity | ~9.8 W/m·K (RT) |
| Electrical Resistivity | ~1.31 μΩ·m |
| Specific Heat | ~0.427 J/g·K |
| Magnetic Properties | Non-magnetic (Austenitic) |
Applications of Inconel 625
- Marine engineering: seawater piping, pumps, valves, propeller systems
- Chemical processing: reactors, heat exchangers, scrubbers, spray towers
- Aerospace: exhaust ducts, engine components, insulation
- Energy sector: nuclear reactor components, FGD systems, heat recovery
- Medical & food: high-purity process systems, clean piping
Advantages of Inconel 625
- Outstanding resistance to seawater, oxidizing acids, phosphoric acid, and chloride media
- Excellent high-temperature oxidation and thermal fatigue resistance
- Exceptional weldability with low risk of cracking
- High strength without precipitation hardening—good for structural fabrication
- Strong resistance to stress corrosion cracking
- Excellent formability and cold workability
Limitations of Inconel 625
- Higher material cost
- Lower strength than precipitation-hardened alloys like Inconel 718
- May experience structural degradation under prolonged exposure above 980°C
- Not ideal for highly reducing acids (where C276 may perform better)
FAQ About Inconel 625
Yes, it provides exceptional seawater corrosion resistance, making it ideal for marine engineering and desalination.
625 is solid-solution strengthened and excels in corrosion resistance. 718 is precipitation-hardened and offers higher strength but slightly less corrosion resistance.
Yes, it has excellent weldability, with little risk of hot cracking or post-weld embrittlement.
Yes, it performs reliably up to 980°C, with good oxidation and thermal cycling resistance.
Summary
This article introduces Inconel 625, explains the alloy, and discusses its composition, properties, and applications. For more information about Inconel 625, please get in touch with an MT.BOLTS representative.
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