Current Issue : April-June Volume : 2023 Issue Number : 2 Articles : 5 Articles
The introduction of external surface features on mating contact surfaces is an effective method to reduce friction and wear between the contact surfaces. The tribological properties of the contact surfaces can be improved by controlling the geometrical parameters (shape, size, depth) of the surface texture effectively. In the present study, the tribological properties of Al6061-T6 cylindrical workpieces with various micro-dimple-texture geometries and an AISI 52100 steel stationery block are tested experimentally, in a rotating cylinder-on-pin configuration of the friction test. The dual-frequency surface texturing method is employed to create micro-dimple textures using a polycrystalline diamond tool. The effect of a hierarchical micro-dimple texture is then investigated under boundary lubrication conditions. Hierarchical micro-dimples, with an increase in length, show a lower friction coefficient under high load and sliding speed conditions. Secondary hierarchical nano-structures help in improving the tribological characteristics by generating an additional hydrodynamic lift effect....
Ta2O5 was deposited on quartz glass and Si substrates as a protective coating. The inherent RF magnetron sputtering power of 140 W was maintained during the deposition process. During the deposition process, amounts of 5%, 10%, and 15% of N2 were injected, and the total sputtering gas (N2+Ar) flow was kept at 40 sccm. The microstructure and surface morphology of the coatings were characterized, and the friction and wear experiments of the coatings were carried out. The results show that the coatings’ surface is smooth and the main chemical compositions are Ta, O, and N. The maximum average roughness of the coatings was prepared by pure argon sputtering. It is proved that the introduction of N2 reduces the surface roughness of the coatings and increases the surface hardness and elastic modulus of the coatings. Adhesive wear and brittle fracture are the two main wear forms of coatings. The wear debris is mainly composed of columnar particles and a flake structure....
The mechanical properties and tribological behavior of ductile iron tempered at different temperatures were investigated. The tempered sample was composed of spheroidal graphite, α phase, and carbides. The strength and hardness decreased near-linearly but the plasticity increased with the increase of tempering temperature, which was mainly because carbon atoms precipitated from martensite and thus reduced the distortion of martensite. Wear tests indicated that the friction coefficient of the sample tempered at 420 ◦C decreased first and then increased with the increasing loads and exhibited the lowest friction coefficient of 0.37. No obvious change was detected for the friction coefficient of the sample tempered at 500 ◦C at different loads. The friction coefficient of the sample tempered at 580 ◦C increased to a stable value with the increase of loads. The wear rate of tempered ductile iron was increased with the increase of tempering temperature, which indicated that hardness was the critical factor for wear properties of ductile iron. The main wear mechanisms of tempered ductile iron were adhesive and abrasive wear. Adhesive wear was predominant for the sample tempered at low temperature but was gradually replaced by abrasive wear with the increase of tempering temperature and normal loads....
The thermomechanical and tribological properties of graphene (GNS)-reinforced NR were investigated using molecular dynamics (MD) simulations. The amorphous molecular dynamics models of two nanocomposites, i.e., natural rubber (pure NR) and graphene/natural rubber (GNS/NR), were established. In addition, the thermodynamic properties of the two materials, before and after the incorporation of graphene into the natural rubber matrix, were investigated through analytical comparison. The results showed that after the graphene was added to the rubber matrix as a reinforcing material, the elastic modulus and shear modulus were increased by 110% and 94.8%, respectively, the tensile property was increased by 178%, the overall thermal conductivity of the composite system was increased by 59%, the glass transition temperature increased from 223 K to 236 K, and the rigidity of the material matrix was significantly improved. The inherent interactions and wear mechanisms of the polymer nanocomposites were discussed at the atomic scale by analyzing the changes in temperature, atomic velocity, relative atomic concentration, and radial distribution functions at the friction interface in the thickness direction....
B4C-particle-reinforced Al (B4Cp/Al) composites are widely used in various areas, e.g., armors, electronic packaging and fuel storage, owing to their several outstanding properties including high specific rigidity, excellent wear resistance and light weight. Selective laser melting (SLM) is favored in manufacturing complex components because of its high raw material utilization rate and high efficiency. In this work, a B4Cp/Al composite was successfully synthesized by SLM, and the effects of one of the most important parameters, scanning speed (100–700 mm/s), on the phase composition, density, microhardness and tribological properties of the samples were investigated. The microhardness, relative density and dry-sliding wear resistance of as-prepared B4Cp/Al composites were improved with the decrease in scanning speed, and the sample fabricated at a scanning speed of 100 mm/s exhibited a relative density as high as about 97.1%, and a maximum microhardness of ~180 HV0.1 (approximately six times more than that of the SLM-formed pure Al sample, 31 HV0.1), a minimum wear rate of 4.2 × 10−5 mm3·N−1·m−1 and a corresponding friction coefficient of 0.41. In addition, abrasive wear, adhesive wear and oxidation wear were found to be behind the overall wear behavior of as-prepared B4Cp/Al composites....
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