Effects of Case Depth and Relative Radius of Curvature on Surface Durability of Case-Hardened Chromium Molybdenum Steel Roller

In this report, effects of case depth and relative radius of curvature on surface durability of case-hardened chromium molybdenum steel roller are experimentally clarified. The experimental results are discussed by amplitude of ratio of shear stress to Vickers hardness considering hardness and residual stress distributions of roller. Surface failure mode in this experiment was spalling due to the crack having the point of origin beneath the surface. Depth of spolling crack agreed well with depth of the maximum amplitude of the ratio of orthogonal shear stress to Vickers hardness. Surface durability of the roller tended to increase as the case depth increased, but in the case of too deep case depth it was not so high. And the surface durability tended to decrease as the relative radius of curvature increased.