Rolling fatigue life of supercarburized steel for rolling bearing materials

摘要

The effectiveness of supercarburization as one means to improve the life of a bearing in dirty oil was studied. As a result, the following became clear. (1) Life in dirty oil was improved 2.5 times by supercarburization. (2) This was because the surface hardness was increased and the wear resistance was improved. (3) There is the possibility that the flaking of supercarburized steel does not originate in the surface, but in the subsurface. Carbide acting as a stress concentration source can be considered as a reason for this. (4) The coarsening of the carbide leads to stress concentration at the starting point and life decreases along with an increase in the diameter of the carbide particles. (5) A crack that occurs due to flaking develops without regard to the carbide and the matrix, and carbide does not act as a defect in the crack propagation region. In conclusion, I would like to express my deep appreciation to Chiba University Emeritus Professor (presently Shonan Institute of Technology Professor) Junzo Okamoto for his valuable advice related to the study of friction force and shearing stress in preparing this paper.