高周波焼入れ材のピッティング寿命に及ぼす有効硬化層深さとケイ素含有量の影響

抄録

The influence of effective case depth(ECD) and silicon content on contact fatigue strength of induction hardened steels was investigated by roller pitting test. The pitting life increases with decreasing ECD, when ECD is large enough to prevent plastic deformation in core. The reason is that absolute value of residual compressive stress increases with decreasing ECD and initiation and propagation of surface cracks are suppressed by residual compressive stress. The pitting life is improved by increase in silicon content. Decrease in hardness of hardened case causes slip bands and voids by alternating load. The slip bands and voids become crack propagation path. Silicon suppresses softening of hardened case during roller pitting test and improves pitting life.