Tribological and Microstructural Characterization of Ultrafine Layers Induced by Wear in Ductile Alloys

This work studies the ultrafine subsurface layer produced in Al-Sn and Cu alloys in contact with AISI9840 steel. The tribological tests were conducted at room temperature without lubrication in a coaxial tribometer. A first microstructural characterization was performed using conventional scanning electron microscopy (SEM) and atomic force microscopy (AFM). Grain refinement mapping was performed by means of Electron Backscattering Diffraction (EBSD). The wear process, during which tribolayers are formed, leads to significant differences between the structure of the sub-micrometrical layer below the tribolayer and that of the bulk. SEM images show severe mechanical mixing in the surface of the worn zones, whereas EBSD observations allow identifying the mechanically homogenized layers as a sub-micro-crystalline material with a cellular structure aligned along the sliding direction.