Fatigue and recrystallization evolution of carbide-free bainitic layer under high-stress rolling sliding contact

Abstract

The rolling contact fatigue behavior of a newly developed bearing steel with carbide-free bainite, modified by a combination of tungsten inert gas surface melting and subsequent isothermal transformation was investigated. The rolling sliding tests were conducted to determine the vibration response and rolling contact fatigue life. The rolling contact fatigue life of the bainitic layer is 6.623 × 106 cycles, significantly higher than that of the commercial GCr15 steel sample (4.496 × 106 cycles). Focused ion beam technology and transmission Kikuchi diffraction studies on fatigue-tested samples showed that the toughness of the bainitic layer could be improved by the bainitic ferrite and retained austenite, which recrystallizes and forms nanocrystals during the rolling contact fatigue process. Furthermore, high-resolution transmission electron microscope study elucidated that the bainitic layer has better dislocation slip ability and is more prone to recrystallization on the rolling contact fatigue surface, preventing the rapid expansion of fatigue cracks. Moreover, the effect of dissolution of the Fe3C in GCr15 steel on the structure of distorted body-centered cubic crystals and pitting defects was also comparatively investigated.