Third-body and crack behavior in white etching layer induced by sliding-rolling friction

The tribologically transformed structure of the white etching layer (WEL) always appears with some cracks accompanying microstructural evolution under friction. This work investigated crack behavior with the existence of WEL on pearlitic steel after rolling-sliding friction tests. The WEL microstructure was characterized using scanning electron microscopy, nano-indentation, focused ion beam, and transmission electron microscopy. According optical images, the WEL zone could be divided into white and yellowish zones; cracks existed at the boundary separating these two zones. The deformation degree of the cementite structure caused color differences in optical images and inhomogeneous chemical composition distributions in the same WEL zone. For cracks initiated and propagated at the WEL colony boundary, crack holes remained unconnected along the plastic deformation line.