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This paper is focused on the effects of the separately applied laser heat treatment (LHT) and ultrasonic impact treatment (UIT) and the combined LHT + UIT process on the wear and friction behaviors of the hardened surface layers of the tool steel AISI D2. In comparison with the initial state, wear losses of the treated specimens after long-term wear tests were decreased by 68, 41, and 77% at the LHT, UIT, and combined LHT + UIT processes, respectively. The Abbott–Firestone bearing curves were used to analyze the material ratio and functional characterization (bearing capacity and oil capacitance) of the studied surface specimens. The wear losses registered after short (15 min) tests correlate well with the changes in experimental surface roughness Ra, and the predictive Rpk, and bearing capacity BC parameters, respectively, evaluated using the Abbott–Firestone curves and Kragelsky–Kombalov formula. The wear losses after the long-term (45 min) tests are in good correlation with the reciprocal surface microhardness HV and with the WL and WP wear parameters, respectively, estimated using Archard–Rabinowicz formula and complex roughness-and-strength approach. The observed HV increase is supported by nanotwins (LHT), by dense dislocation nets (UIT), and by dislocation cells/nanograins fixed with fine carbides (LHT + UIT) formed in the surface layers of the steel. [ABSTRACT FROM AUTHOR]

Paper compares wear resistances and friction behaviours of the surface composite layers produced on aluminium of commercial purity (1060) and Al-6Mg aluminium alloy (~5056) using ultrasonic impact treatment (UIT). Atomized powders containing quasicrystalline (QC) phases of two systems, Al63Cu25Fe12 (QC1) and Al93Fe3Cr2Ti2 (QC2), and SiC powder were used as reinforcing media. The layers of composite are formed owing to mechanical mixing of the matrix alloys and reinforcing powders fed into a zone of severe plastic deformation induced by the UIT process. Wear and friction behaviours in inactive liquid paraffin were studied at reciprocating sliding of a Si3N4 semi-spherical indenter in quasi-static and dynamic regimes. It is shown that the QC1 and QC2 reinforcing particles enhance the wear resistance of the 1060 matrix alloy by 10-30% and 50%, respectively. As compared to Al-based layers, the wear resistance of the Al-6Mg alloy matrix composite layers is five times better in static wear conditions and on the order of magnitude better in the dynamic regime. The relative improvement in wear resistance of QC2 reinforced layer (55%) is comparable to that of the SiC reinforced layer (62%) in the quasi-static regime, and exceeds it in dynamic one (34% vs 23%). Laser confocal microscopy shows that the coarse QC1 and SiC reinforcing particles underwent fracture at the production process or at wear test that increased the friction force and deteriorated the wear resistance of the Al-6Mg matrix alloy. Wear behaviour of the produced composite layers is shown can be successfully described by the modified Archard equation that accounts both for the composite hardness and the ratio of the particles fracture toughness and volume fraction to the square root of the particle size. In spite of very low fracture toughness of quasicrystals, the nano-QC particles can support local plasticity, better interfacial bonding, and higher strengthening, and they, therefore, can be used as reinforcing media in the aluminium matrix composites, which would ensure high wear resistance. Considering the wear and friction behaviours of these composite layers the reinforcing efficiency of the aluminium based nano-QC particles is concluded to be comparable with that of the SiC particles. [ABSTRACT FROM AUTHOR]