Influence of Shot Peening on Surface Durability of Plasma Case-Hardened Sintered Powder Metal Gears

In order to investigate the influence of shot peening on the surface durability of sintered powder metal gears, the plasma case-hardened sintered powder metal rollers and gears shotpeened with different condition were fatigue-tested under a sliding-rolling contact condition. The hardness, the compressive residual stress and the surface roughness of the rollers and gears increased by the shot peening. The failure mode of the rollers and gears was mainly spalling. The main crack of the failed rollers and gears propagated through the pores below the roller and the tooth surfaces. The surface durabilities of the lightly shot-peened rollers and gears were higher than those of the other rollers and gears. While, the surface durabilities of the strongly shot-peened rollers are lower than that of the unpeened roller because of the increase of the surface roughness and the deformed sharp pore by the strong shot peening.