Inconel > Tubing > Inconel 625

Type 625 is a nickel-based super alloy that possesses excellent resistance to oxidation and corrosion in a broad range of environments. Additionally this alloy has outstanding strength and toughness at temperatures ranging from cryogenic to 2000 degrees Fahrenheit. This alloy possesses a high degree of formability and shows better weldability than many other highly alloyed nickel based materials.

This nickel-chromium-molybdenum wrought alloy is an excellent general purpose material for elevated temperature use in high strength, oxidation problem applications. It also has excellent corrosion resistance to many acids and resists intergranular attack and stress-corrosion cracking.

Applications: The alloy finds use in high temperature applications such as heat exchangers and gas turbine components. Because of its good corrosion resistance it is also used in wet scrubbers and some acid process equipment.

Machinability: May be machined by conventional means. However the alloy tends to work harden ahead of cutting and rigid tooling is essential to avoid chatter and work hardening in front of the tool edge.

Forming: This alloy can be cold formed by conventional means and tooling. The alloy does work harden during cold working with an attendant increase in strength. This increase in strength may be of value for moderate temperature applications and, in these instances, the formed parts can be left in the cold work hardened condition.

Welding: Welding is readily accomplished using matching alloy filler metal for the conventional welding techniques.

Heat Treatment: The alloy is furnished in the solution annealed condition. This is done at 2150 F for sufficient time dependent upon section thickness. Following the anneal the alloy may be air cooled.

Forging Hot forging can be done by heating the billet to 2100 – 2150 F, but not over 2150. Heavy forging may then be done down to a billet temperature of 1850 F and light forging down to 1700 F. Final reductions of 15 to 20% minimum are recommended to maintain proper grain structure.

Hot Working: Hot forming may be done by heating the alloy to 2150 F. Because this alloy is engineered for good strength at high temperatures it will resist hot deformation and therefore requires powerful equipment to perform hot forming.

Cold Working: The alloy can be cold formed by conventional methods and tooling. See also the comments under “Forming” regarding work hardening.

Annealing: Because the alloy work hardens during hot or cold forming it may be necessary to anneal such parts in order to complete forming operations. Annealing is done at 1800 to 2000 F and air cooled. Stress relief of cold worked parts may be accomplished at 1100 to 1400 F.

Aging: The alloy derives its strength from its basic chemical composition. Thus aging or precipitation hardening is not applicable as a heat treatment.

Tempering Not applicable.

Hardening: Cold working does harden the alloy and improve strength, dependent upon the amount of cold working. The alloy can be used in this higher strength cold worked condition or may be annealed at 2150 F to restore original mechanical properties.