Quenching of aerospace forgings from high temperatures using air-assisted, atomized water sprays

Abstract

The nickel-based superalloy or titanium materials used in the aerospace industry are cooled from high temperatures during the heat treatment process to obtain appropriate strength properties. However, unacceptably high residual stresses can be developed in some situations if the rate of cooling is too high so that air-assisted, atomized water sprays have been suggested as an alternative to the widely used techniques of quenching in oil or water. Thus, this article examines two aspects of the use of air-water sprays for quenching aeroengine forgings. First, basic experimental heat transfer data are presented for a wide range of water flows and for surface temperatures up to approximately 850°C, for both plane and recessed surfaces. Second, the heat transfer data are used in numerical simulations to study the influence of nonuniform spray distributions on the residual stress patterns in a typical forging.

Ultra Fast Cooling of a Hot Steel Plate by Using High Mass Flux Air Atomized Spray

“…The difficulty in achieving fast cooling rate at high initial surface temperature (∼900°C) is the Leidenfrost problem if water is used as a coolant. Due to the aforesaid problem, a vapor film covers the hot plate and as a result the heat transfer rate from the hot surface drastically reduces 8, 9. Hence, the film boiling has been the subject of investigations.…”

Characterization and modeling of quenching-induced residual stresses in the nickel-based superalloy IN718

“…[9] The superalloys are used for the critical rotating parts for turbinedisc applications, e.g., jet propulsion and electricity generation, where fatigue fracture is a possibility that must be accounted for in the design process. The forgings from which turbine discs are fabricated are machined using high-speed lathes in an intricate way, such that the finished part contains thin sections such as drive arms and webs.…”