Comprehensive Guide to Nickel-Based Superalloys: Inconel 625 (UNS N06625/W.Nr. 2.4856)
What is Inconel 625?
Inconel 625 is a nickel-based superalloy with a density of 8.4 g/cm3 and a melting point of 1290-1350°C. It has excellent resistance to corrosion by inorganic acids and to a variety of corrosive media in oxidizing and reducing environments.
Alloy 625 exhibits excellent corrosion resistance in many media. It has excellent resistance to pitting, crevice, intergranular and erosion in chloride media.
Designated as UNS N06625 or W.Nr. 2.4856, Inconel 625, also known as Alloy 625, is a nickel-chromium-molybdenum alloy with the addition of niobium, which works with molybdenum to harden the alloy matrix, thereby providing high strength without the need for intensive heat treatment. The alloy can resist a variety of severe corrosive environments, especially pitting and crevice corrosion, and has excellent fatigue strength and resistance to chloride ion stress corrosion cracking. Inconel 625 can be used in chemical processing, aerospace and marine pipelines, pollution control equipment and nuclear reactors. It can usually be used at oxidation temperatures up to 980°C [1800°F].
Inconel 625 metallographic structure
625 is a face-centered cubic lattice structure. After long-term heat preservation at 650℃, carbon particles and unstable quaternary phases will precipitate and transform into a stable Ni3 (Nb, Ti) rhombohedral lattice phase. After solid solution strengthening, Mo and Nb in the Ni Cr matrix will improve mechanical properties, but plasticity will decrease.
Inconel 625 Corrosion Resistance
625 alloy shows excellent corrosion resistance in many media. It has excellent resistance to pitting, crevice corrosion, intergranular corrosion and erosion in chloride media. It has good resistance to corrosion by inorganic acids, such as nitric acid, phosphoric acid, sulfuric acid, hydrochloric acid, etc. It also has corrosion resistance to alkali and organic acids in oxidizing and reducing environments. It effectively resists chloride reduction stress corrosion cracking. It has high corrosion resistance to seawater and salt solutions, and also has high high temperature resistance. There is no sensitivity during welding. It is resistant to carbonization and oxidation in static or circulating environments, and resistant to corrosion by chlorine-containing gases.
Typical applications:
1. Components of organic chemical processes containing chlorides, especially when using acyl chloride catalysts.
2. Digesters and bleaching tanks in the pulp and paper industry.
3. Absorbers, reheaters, flue gas inlet baffles, fans (wet), agitators, guide plates, flues in flue gas desulfurization systems.
4. Equipment and components used in the manufacture of acidic gas environments.
5. Acetic acid and acetic anhydride reaction generators.
6. Sulfuric acid condensers.
