Introduction
High temperature alloy forgings should receive appropriate heat treatment in order to obtain the excellent mechanical properties and to develop the desired shape and dimensions. Heat treatment of high temperature alloys consists of quench annealing, solutioning, and aging. This paper outlines the heat treating protocol for high temperature alloy forgings, with special emphasis on the quench annealing, solutioning, and aging.
Quench Annealing
Quench annealing of high temperature alloy forgings is typically done to balance material properties and reduce energy expenditure during processing. The process involves the heating of the forgings to a temperature where grain boundaries move, creating better grain flow. As the forging is cooled, it is cooled to a temperature below the critical temperature of the material, resulting in the dissolution of harmful precipitates and the formation of new as-quenched grains.
Solutioning
Solutioning of high temperature alloy forgings begins by heating the forging to a temperature above the alloys maximum solid solution temperature, which is known as the “super-heat temperature.” The alloy must remain at this temperature for a set amount of time before it is quenched. This serves to dissolve any hardening precipitates within the alloy, allowing them to be recrystallized during the next step, aging.
Aging
Aging of high temperature alloy forgings is done to allow the dissolved hardening precipitates to be recrystallized and form new, uniformly sized crystals. This step also strengthens the structure of the high temperature alloy forging and increases its fatigue strength.
Conclusion
Heat treatment of high temperature alloy forgings is essential to obtaining optimal mechanical properties and geometric sizes. The process consists of quench annealing, solutioning, and aging. Quench annealing is used to balance material properties and reduce energy expenditure. Solutioning is done to dissolve any hardening precipitates, and aging is done to recrystallize those precipitates and strengthen the structure of the forging. With proper heat treatment, high temperature alloy forgings can achieve superior mechanical properties and dimensional stability.
