Microstructural changes in Bearing Steel during rolling Contact Fatigue Test
최해창Hae Chang Choi, 김석우Suk Woo Kim, 남원종Won Jong Nam
Abstract
Microstructural changes in STB2 bearing steel caused by rolling contact fatigue test, were investigated using optical and scanning electron microscopy. Dark area, butterfly structures and plate-like carbides were found in the area below the flaking. Rolling contact caused the formation of Dark area in the subsurface area of contact in the region of maximun Hertzian stress. Most subsurface cracks were initiated at the region of Dark area. Butterflies found only at the oxide inclusions, were frequently associated with cracks. Plate-like carbides acted as the potential crack initiation site responsible for the flaking. The growth of plate-like carbides was caused by the carbon diffusion by rolling stress between not only oxide inclusions but also fine residual carbides.