Abstract
In order to compare the fatigue strength of powder forged gears with that of steel gears, the case-hardened powder forged rollers and gears with different Ni content and the case-hardened steel rollers and gears were fatigue-tested under a sliding-rolling contact condition. The surface hardness of the powder forged rollers and gears with the lower Ni content was almost equal to that of the steel rollers and gears. On the other hand, the hardness of the powder forged rollers and gears with the higher Ni content was smaller than that of the other rollers and gears. The compressive residual stress and the surface roughness of the powder forged rollers and gears were about equal to those of the steel rollers and gears. The failure mode of the test rollers was mainly spalling, and that of the test gears was mainly pitting. Using the relationship between the maximum amplitude of the ratio of stress to Vickers hardness and the fatigue life of the rollers and gears, it was denoted in this experimental range that the fatigue life of the powder forged rollers and gears with the higher Ni content was longer than that of the steel rollers and gears.
