Residual stress distribution and fatigue strength of carburized gear steel. (1st Report, The effects of intergranular oxidation and shot peening on the bending strength in the case).

Abstract

The main purpose of this paper is to clarify the effect of residual stress on thee bending strength of carburized gear steel whichc has an intergranular oxidation layer in the top surface and also to study the effect of residual stress by shot peening on the bending strength. The residual stresses were measured by an X-ray diffraction method. Bending fatigue tests of gear model specimens were carried out under the condition of constant stress range. Correlation samong relation stress, hardness, and the bending strength were found that there were good correlations between residual stresses near the surface layer and the bending strength, and the latter was related to the hardness of the surface and the core in both cases of carburized and shot-peened gear steels. It was also found that it was important to remove the rough surface of the intergranular oxidation layer of carburized material and harden the surface layer by means of shot peening from the point of view of the fatigue strength.