ATI 625HP™ alloy (UNS N06626) is an austenitic nickel-base superalloy possessing exceptional fatigue resistance. ATI 625HP™ alloy was developed especially for bellows applications. It also has excellent resistance to oxidation and corrosion over a broad range of conditions, including jet engine environments and in many other aerospace and chemical process applications. The alloy has outstanding strength and toughness at temperatures ranging from cryogenic temperatures to 2000°F (1093°C).

The ATI 625HP™ alloy is a restricted composition, vacuum melted variant of the widely known alloy 625 (UNS N06625) material. It derives its strength from the solid solution strengthening effects of molybdenum and columbium on the nickel-chromium matrix. These elements also contribute to the alloy's outstanding corrosion resistance. Although the alloy was developed for high temperature strength, it also provides a high level of general corrosion resistance to a wide range of oxidizing and non-oxidizing environments. The levels of chromium and molybdenum provide excellent resistance to chloride ion pitting and the high level of nickel provides resistance to chloride stress corrosion cracking. The material possesses a high degree of formability and shows better weldability than many of the other highly alloyed nickel-base alloys. The alloy is resistant to intergranular corrosion even in the welded condition.

ATI 625HP™ alloy is produced by a two-step melting process that includes a consumable electrode remelting procedure. At least one of these steps is performed in vacuum.