X線回折環分析装置によるピーリング損傷の評価

抄録

This paper introduces the evaluation of rolling contact fatigue (RCF) under insufficient lubrication condition for carbonitrided bearing steel, JIS SUJ2. The progression of RCF was evaluated based on equivalent stress, retained austenite and the degree of martensite grain orientation which were characterized by three parameters: σ_eq, γ_R and S/S₀, respectively. We calculated σ_eq using a tri-axial residual stress obtained by the Sasaki-Hirose method. The S/S₀ was defined as the variation of peak intensities for the central angle of the X-ray diffraction ring. In order to confirm quantitativity of γ_R, two types of X-ray devices ware used. These parameters were compared with specimens subjected to standard heat treatment of SUJ2. As a result, the following knowledge was obtained. Carbonitride caused larger residual stresses and delayed the beginning of increasing of S/S₀. In addition, the peeling area ratio at the number of cycles of 10⁶ was smaller as compared with standard heat treatment specimen. Furthermore the γ_R remained until the end of the test. These results were due to the effect of nitrogen dissolved in steel.