An Evaluation of Atmosphere and Vacuum Carburizing Methods for the Heat Treatment of Gears

Vacuum carburizing has proven itself a robust heat treatment process and a viable alternative to atmosphere carburizing. Many companies are currently evaluating which technology to invest in for the future. The work reported here will provide technical reasons why vacuum carburizing should be chosen.

Gear manufacturers of heavy duty, off-road transmissions and related equipment such as Twin Disc Corporation have found numerous benefits to substitute vacuum carburizing with high gas pressure quenching technology for either atmosphere or vacuum carburizing with oil quenching technology. This paper will present scientific data in support of this choice.

Of paramount importance is lowering unit cost that can only be achieved by improved dimensional control and cost effective manufacturing methods. Figures 1 and 2 compare an atmosphere carburized gear requiring press quenching to achieve dimensional tolerances in a “one piece at a time” heat treating operation with a vacuum carburized load of gears that have been high gas pressure quenched within required tolerances.

The benefits achieved by this process can be realized in high volume, critical component manufacturing operations. The results are parts with enhanced hardness and mechanical properties.