Gas Quenching with Helium

Gas quenching in vacuum furnaces is an increasingly attractive option because it has a low environmental impact and the least distortion of parts being treated. Whilst nitrogen is by far the most common quenching gas, helium is a viable option where higher cooling rates are required, particularly for carburised components. This paper explores the improvements in gas quenching technology that allow components manufactured from standard carburising steels to be quenched with high-pressure helium and illustrates the improvements it offers over high pressure nitrogen quenching. As helium is an expensive rare gas, recycle systems make its use more economically attractive. The factors that need to be taken into account when designing such systems, including the necessity for purification, are discussed. Sources of helium and the means of delivery, particularly in Asia, are also covered.