Ionic Liquids as New Quenching Media for Aluminium Alloys and Steels*

Abstract

Abstract Quenching in vaporising liquids is mostly affected by the Leidenfrost effect, causing avoidable residual stresses and distortion. Molten salts and molten metals provide a quenching without any Leidenfrost effect, but need to be operated at high bath temperatures with a high effort for cleaning the quenched components. In this work ionic liquids (salts with melting temperatures below 100 °C) are investigated as quenching media with respect to cooling power, homogeneity and thermal stability. Aluminium and steel cylinders have been quenched in baths of different ionic liquids with varying compositions and bath temperatures showing almost no Leidenfrost effect. The time-temperature curves have been recorded and the heat transfer coefficients were determined. It was shown, that the cooling power of ionic liquids could be increased by limited water addition without any Leidenfrost effect and is sufficiently fast even for quench sensitive alloys. Further investigations on aluminium samples with a complex profile show that quenching in ionic liquids causes less distortion compared to water quenching.