Modelling the gas quenching of a carburised gear

P. F. Stratton:

Proceedings of the 8th Seminar of the International Federation for Heat Treatment and Surface Engineering , IFHTSE 2001, Dubrovnik- Cavtat, Croatia, 12 – 14 September 2001.

The application of gas quenching to a single component or single layers of components that have been heated in vacuum or conventional atmosphere furnaces has been proposed to achieve higher quenching rates than those possible with conventional multi-component gas quenching.  Such treatments meet the need for a clean, non-toxic quenching medium that leaves no residues to be removed after processing.  The processing of single components allows the operator complete control of the quenching intensity both locally and generally.  Moreover the quenching rate may be changed during the R. Nöbauer quenching cycle.
Modelling has shown that by using the delivery pressure available from liquid nitrogen storage systems it is possible to generate the velocities required to produce at least oil-like quenching characteristics at a surface using an array of gas jets.  The work reported in this paper extends that modelling to a typical gear.  The design of the jet array required to achieve an effectively uniform quench rate is described.  The cooling rates resulting from the use of several nitrogen/hydrogen mixtures is reported, together with the microstructures that would be expected in a typical carburised gear.

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