Inconel 625
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INCONEL® 625 is a nickel-based superalloy with excellent resistance to corrosion and oxidation at both high and low temperatures. The alloy is composed of chromium, molybdenum, and niobium, providing high tensile strength, good creep resistance, and outstanding resistance to stress corrosion cracking and pitting – even in chloride-rich and marine environments. No heat treatment is required, as its mechanical properties are achieved through its chemical composition.
Recommended filler material for welding is INCONEL® 625 and INCONEL® 112 electrodes.
General Material Description:
Type: Nickel-chromium-molybdenum alloy with added niobium
Structure: Austenitic, solid solution hardened
Developed: 1960s for steam lines; now standard in offshore, chemical, aerospace, and energy industries
Alternative names: UNS N06625, Werkstoff 2.4856, ASTM B443/B446, EN 2.4856, Haynes 625, Nicrofer 6020
Key Advantages:
Exceptional corrosion resistance in both oxidizing and reducing environments
Resistant to pitting, crevice corrosion, and chloride stress corrosion cracking
High mechanical strength from cryogenic temperatures up to 982°C
Excellent weldability with no risk of intergranular cracking
Good machinability despite its high strength
Drawbacks / Limitations:
Higher cost compared to stainless steel and simpler nickel alloys
Difficult to machine – requires specialized tools and processes
Not ideal for highly reducing environments with concentrated hydrochloric acid
Applications by Industry and Value:
Offshore / Marine: Pipes, valves, pumps – thanks to resistance to seawater and chlorides
Chemical Processing: Heat exchangers, reactors – resists acids and bases
Aerospace: Exhaust systems, thrust reversers – high temperature and oxidation resistance
Energy / Nuclear: Heat exchangers, pressure vessels – stability at high temperatures
Waste Management: Incinerators, flue gas treatment – resistance to corrosive gases
General Corrosion Description:
Nearly immune to corrosion in freshwater, seawater, neutral salts, and alkaline media
High resistance to pitting and crevice corrosion in chloride environments
Resistant to intergranular corrosion after welding
Stable in both oxidizing and reducing acids, including nitric and sulfuric acid
Environments Where the Material Performs Well:
Seawater (even at high temperatures)
Oxidizing acids (nitric acid, phosphoric acid)
Reducing acids (sulfuric acid, hydrochloric acid)
Alkaline solutions and organic acids
Chloride-rich environments – resists stress corrosion
Environments Where the Material Should Be Avoided:
Highly concentrated hydrochloric acid at elevated temperatures
Hydrofluoric acid and certain molten salts
Extremely reducing environments with no oxygen availability
Technical Material Properties:
Property (Typical Value)
Yield Strength (0.2% offset): 414–517 MPa
Tensile Strength: 827–1034 MPa
Elongation at Break: 30–60%
Density: 8.44 g/cm³
Elastic Modulus: ~207 GPa
Thermal Conductivity: ~9.8 W/m·K
Service Temperature Range: -196°C to +982°C
Weldability: Very good
Machinability: Moderate – requires specialized tools
Hardness (Brinell): 145–220 HB