Inconel Alloy 625 (UNS N06625) with a nominal composition of 58% Nickel, 20% Chromium, 6% Molybdenum and 10% Iron is a precipitation hardenable, Nickel-base alloy with excellent strength and corrosion resistance at high temperatures. Inconel 625 is used in a variety of industries including aerospace, process equipment and high temperature fastening applications.
Inconel 625 is noted for its resistance to corrosion in a wide range of environments and for its strength at high temperature and pressure. Its oxidation resistance is higher than that of other Nickel-base alloys, except for those based on Titanium. It is especially resistant to stress corrosion cracking and pitting in high temperature environments.
Inconel 625 can be readily formed using common forming processes, but it will require special care due to its precipitation hardening. Inconel 625 is usually supplied in the hot rolled, annealed and pickled condition with a bronze-like, soft luster and mechanical properties that can be hardened significantly by heat treatment. Cold forming of Inconel 625 is possible, but it will require extra care in order to prevent cracking.
Inconel 625 is commonly used in applications where high strength and corrosion resistance are required at high temperatures. It can be found in components such as turbine blades and flanges, exhaust systems and heat exchangers, as well as pumps and valves used in oil and gas production. Inconel 625 can also be used in jet engines, pressure vessels, shafts and fasteners.
In order to ensure the desired properties of Inconel 625, heat treatment is often used. As alloys of Nickel base alloys are sensitive to the presence of sulfur and phosphorus, annealing is usually done in hydrogen-disulfide to prevent hot-shortness in parts that are subsequently cold worked. Inconel 625 can also be solution treated, for example by solution annealing in which the temperature of the alloy is raised to a temperature above the beta-transus, typically between 1140°C and 1150°C, and then rapidly cooled.
To further improve on the mechanical properties of Inconel 625, it is also possible to use double aging treatment, such as solid solution treating followed by cold working and double-aging treatment. In double aging treatment, the material is rapidly quenched from the original solution treatment temperature to a temperature below the beta-transus, typically around 1038°C, and then slowly cooled with the goal of completely transforming the solution treated material into the gamma-prime structure which exhibits increased hardness. This particular type of heat treatment is typically used to further improve corrosion and fatigue resistance of the material.
Inconel 625 is a valuable nickel-base alloy that is used in a variety of industries and applications. Its excellent corrosion resistance, strength at high temperatures and hardness is achieved via a combination of heat treatment processes and alloy composition. The combination of solid solution treating and double-aging treatment is often used to further improve the mechanical properties of the material.
