Influence of Shot Peening on Surface Durability of Plasma Case-Hardened Sintered Powder Metal Rollers. Influences of Shot Velocity, Shot Diameter and Shot Hardness.

Abstract

In order to investigate the influence of shot peening on the surface durability of sintered powder metal rollers, the plasma case-hardened sintered powder metal rollers shot-peened with different shot velocity, shot diameter and shot hardness were fatigue tested under a sliding rolling contact condition. The compressive residual stress, the hardness and the surface roughness of the rollers increased and the pores in those were deformed by the shot peening. The failure mode of the rollers was spalling. The failure depth of most rollers agreed almost with the depth near the case-core boundary where the amplitude A(τyz/HV) of the ratio of orthogonal shear stress to Vickers hardness became maximum. In these experiments the surface durabilities of strongly shot-peened rollers were lower than that of unpeened roller, on the other hand those of mildly shot-peened rollers were higher. The frictional force between the rollers and the shear stress below the contact surface generally increase as the surface roughness of the rollers increases. Therefore, it could be followed from above that the mild shot peening which dose not cause too large surface roughness should be selected in order to improve the surface durability of sintered rollers.