Abstract: The flaking failure in rolling contact fatigue (RCF) has been believed to originate from nonmetallic inclusions located beneath the surface. With conventional microscopies, however, damage process in the internal region of materials could not be observed, then they were observed by computed laminography using ultra-bright synchrotron radiation X-ray, and the effects of the shape and the orientation on the RCF crack initiation and propagation behaviors were examined. In every case, cracks were first initiated from surface inclusion, and they propagated to the surface and the thickness direction. After the crack reached a critical distance, horizontal cracks were formed from the vertical cracks, where the normal of the horizontal cracks were perpendicular to the surface, and those of the vertical cracks were parallel to the surface. However, the propagation direction just after the initiation from inclusions depended on the orientation of inclusions relative to the rolling direction.
Authors: Yoshikazu Nakai, Daiki Shiozawa, Shoichi Kikuchi, Takashi Nishina, Hiroshi Kobayashi, Masanori Kurahashi, Taizo Makino, and Yutaka Neishi
Keywords: Rolling contact fatigue, Laminography, Synchrotron radiation