Scale-dependent subsurface deformation of metallic materials in sliding

Using laser speckle decorrelation, TEM, optical microscopy and AFM we study deformation structures generated in subsurface layers of metals and alloys by sliding wear. Strain localization process in sliding wear as well as its effect on sliding-induced structures is considered. As shown, strain localization leads to intense fragmentation in subsurface layers and generation of shear bands in previously fragmented materials. These shear bands first exist at the microscale level under mild wear but may reveal at the mesoscale deformation level when there occurs mild-to-catastrophic wear mechanism transition. The result of such a transition is a thick (tens and hundreds of micrometers) nanocrystalline layer at the surface of metals. Hadfield steel shows another type of tribological behavior when only thin nano crystalline layer is formed. We relate such a behavior to the specificity of fragmentation in this steel. High wear resistance of high manganese steel is analyzed too.