Effect of Abnormal Surface Layer on Tooth Surface Strength of Gas Carburized Gears

The effect of abnormal surface layer produced by gas carburizing on the bending strength of gear tooth has already been reported, although the effect on the tooth surface strength has not been clarified. The authors carried out experiments to study the effect of abnormal surface layer on the tooth surface strength. The test gears with various conditions of abnormal surface layer used in this experiments were prepared by changing the machining process and the material of gears. As a result of experiments, the tooth surface strength of gas carburized gears is affected by the existence of abnormal surface layer. With in the limits of this experiments, it showed that the tooth surface strength of gears with abnormal surface layer is higher than that of gears without abnormal surface layer. Furthermore, it was observed that the quantitative effect of abnormal surface layer on the tooth surface strength is different from the coilditions of abnormal surface layer, i. e. the uniformity and the hardness of slack quenching layer, and the production shape of intergranular oxidation. We concluded from the experiments that the suitable conditions of abnormal surface layer improve thye tooth surface strength of gas carburized gears.