Generation of Submicrometer Particles in Dry Sliding Contact

The generation of submicrometer-sized particles during dry sliding between stainless steel surfaces is investigated by means of a laser spectrometer for particle counting and scanning tunnelling microscopy for asperity topography characterization. It has been found that, when the submicrometer wear increases with increasing sliding distance or with an initially rougher surface, the number of particles having a submicrometer size is a power function of that size. The two wear coefficients in the power function are determined empirically for the case of stainless steel contact. Different from the generation pattern of several-micrometer particles, the generation rate of submicrometer particles continuously increases until reaching the equilibrium surface condition. The asperity topography measurement shows the micrometer-sized asperities also have subasperities whose sizes are about one order of magnitude smaller. An asperity model similar to Archard’s is thus proposed for estimation of submicrometer wear. The dominant wear mechanisms are brittle fracture and plastic deformation combined with adhesion transfer. The asperity contact can be considered as a plastic-elastic deformation system with subasperities deformed plastically all the time and the micrometer asperities first deformed plastically and then deformed elastically because of the significant increase of microhardness on the soft surface in a metal pair. When the microhardness ratio between two rubbing surfaces reaches a stable value, the generation of submicrometer particles reaches the maximum rate and the wear grows steadily.