With metals in sliding friction, in the surface layer (0.01-0.02 mm), ultrafine grained structures are formed, which to a considerable extent determine the tribological properties of the surfaces. The structures can be considered to be nanocrystalline structures (NCS): micro-fragments with large-angle boundaries are 5 to 100 nm in size.
The objects of investigation were the metallic materials with a wide concentration of manganese, having in initial state: BCC, HCP and FCC phases. To compare the obtaining results, the use was made of the tribological characteristics of NCS different alloys: Fe₉₀Mn₁₀, Fe₈₀Mn₂₀, Fe₇₆Cr₁₁Mn₁₃, Fe₆₀Mn₄₀, Fe_63.5Cr₁₈Mn₁₈N_0.5, Fe_68.3Cr₁₉Mn₁₀Si₂N_0.7 and Fe_61.2Cr₁₈Mn₂₀N_0.8, differing in phase composition, structure and value of the stacking fault energy. Tribological test were done at laboratory-scale plants in conditions of sliding friction for the steel-alloy and abrasive-alloy pairs.
The NCS alloys with HCP phase and NCS nitrogen-containing alloys with FCC phase possess low friction coefficients K and high abrasive wear resistance rates epsilon. In this alloys, the developed basal or planar slip characterized by a smaller quantity of the slip systems, condition the lowering of resistance NCS fragments rotation and, as a result, the improvement of tribological properties.
Thus, the essential lowering of friction coefficient K and intensity of adhesion wear Ih, as well as the increase in the abrasive wear resistance rate epsilon of NCS alloys with HCP phase and NCS nitrogen-containing alloys with FCC phase are mainly related to decreasing the quantity of slip systems in nanocrystals of these alloys (n=3). As a result, the dislocations slip to the boundaries of nanocrystals wore easier.