In order to elucidate the mechanism and factors of tooth face pitting, roller tests were carried out. In the tests, the oxidized-nonmartensitic layer, surface roughness, case hardness and residual compressive stress were noted as the material factors, and sliding, oil temperature and viscosity were considered the running condition factors. As a result, the pitting could be classified into two forms according to the crack origin; subsurface origin pitting and surface origin pitting. In the former case, the pitting life coincided with the value estimated from the shear stress and shear strength related to the Vickers hardness. In the latter case, the influence of shot peening could be regarded as the sum of influences due to surface roughness, hardness and residual compressive stress. These factors of shot peening, the existence of the oxidized-nonmartensitic layer and specific sliding determined the life of the surface origin pitting. The life of tooth face pitting could be calculated using these roller test results.

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