The Surface Durability of the Case-Hardened Nickel Chromium Steel and Its Optimum Case Depth

Abstract

In order to clarify the surface durability of the surface hardened steels and the optimum design condition of the surface hardened gears, the carburized and hardened steel rollers were tested with a rolling contact fatigue testing machine. Consequently, it was made clear that there is an optimum case depth for the surface durability and that the crack initiation depth of spalling coincides quite well with the depth where the amplitude of the ratio of orthogonal shear stress to Vickers hardness becomes maximum. By using these test results, the authors introduced a tentative method for calculating the optimum case depth for surface durability of roller pairs which had various relative radii of curvature. And this calculation method was successfully discussed with the practical case-hardened gears.