Abstract: A method of treating low-expansion Fe--Ni--Co superalloys is disclosed in which the alloys are forged at a temperature below the recrystallization temperature and then recrystallized without the use of intervening annealing steps. It is necessary that the warm forging step introduce sufficient strain throughout the Fe--Ni--Co superalloy such that after recrystallizing, the superalloy has a substantially uniform microstructure. Alloys produced by this method exhibit good hydrogen charging embrittlement resistance, good strength and/or rupture ductility in moist air.

Abstract: A process for strengthening heavy, thick-section forgings of precipitation age hardenable iron base superalloys. The process includes initial recrystallization to achieve a uniform grain size, intermediate temperature warm working at controlled strain rates and for limited amounts of deformation, and precipitation heat treating. The controlled warm working conditions avoid further recrystallization, thus preserving the strain hardening which improves the mechanical properties.