Influence of Green Density on Surface Durability of Ion-Nitrided Sintered Powder Metal Rollers

摘要

In order to evaluate the surface durability of ion-nitrided sintered powder metal rollers, the relationship between the surface durability and the green density of the sintered rollers was inves- tigated under a sliding-rolling contact condition. The failure mode of the rollers was spalling due to subsurface cracks. The surface durability of the roller became higher as the green density increased. The pore size and the pore cluster factor represented by the fractal demension became smaller as the green density incleased. Therefore, it could be said that the surface durability of the sintered roller depended on the pore distribution. The spalling failure depth agreed almost with the peak depth of the amplitude A (τ_yz/Hυ) of the ratio of orthogonal shear stress to Vickers hardness. The surface durability was evaluated using the amplitude A (τ_yz) of the shear stress and the hardness Hυ　at the peak amplitude of A (τ_yz/Hυ) . It could be understood that the pore distribution played an important role when the sintered material was designed in terms of the surfface durability.