Hybrids of fluorinated graphite/MoSsub.2 (FGr@MoSsub.2) were prepared via a hydrothermal method and used as lubricating additives to take full advantage of the synergy between FGr and MoSsub.2 in ...carbon-fiber-reinforced polymer (CFRP). The results show a 21.6% reduction in the friction coefficient compared to the neat sample when the CFRP was filled with 1.2 wt.% FGr@MoSsub.2 hybrids. The addition of 1.5 wt.% FGr@MoSsub.2 resulted in a 60.9% reduction in the wear rate compared to neat CFRP. For the 1.2 wt.% FGr@MoSsub.2-reinforced CFRP, the friction coefficient maintained a relatively steady value of approximately 0.46 at various temperatures, indicating frictional stability. However, the wear rate increased by 13.95% at 60 °C compared to that at room temperature. The interfacial bonding force between the FGr@MoSsub.2 hybrid and the matrix, as well as the adhesive force with the surface of the counterpart ball, is improved, caused by the heterostructure of FGr@MoSsub.2, resulting in enhanced mechanical properties and formation efficiency as well as the transfer film on the surface of the counterpart ball. The results suggest that an FGr@MoSsub.2 micro-nano structure is a promising additive to be applied in polymer tribology.
Laser cladding has unique advantages in improving the wear resistance of materials or workpiece surfaces. CeOsub.2 could play a role in promoting the flow of the molten pool and grain refinement ...during the laser cladding process, which is likely to further improve the wear resistance of the coating. In this work, CeOsub.2 was introduced into the MgAlsub.2Osub.4/Fe-based laser cladding coating on the surface of GCr15 steel. The effects of the CeOsub.2 content on the phase composition, microstructure, hardness, and wear resistance of the coatings were also systematically investigated. The results showed that the addition of CeOsub.2 enhanced the continuity of the coating and reduced the size of the MgAlsub.2Osub.4 particles, which was associated with the addition of CeOsub.2’s intensification of the melt pool flow. The metal grain size reduced and then increased as the CeOsub.2 content increased, whereas the hardness and wear resistance of the MgAlsub.2Osub.4/Fe-based coatings increased and then decreased. Compared with the MgAlsub.2Osub.4/Fe-based coating without CeOsub.2, the hardness of the MgAlsub.2Osub.4/Fe-based coating with 1.0 wt% CeOsub.2 increased by 10% and the wear rate decreased by 40%, which was attributed to the metal grain refinement and particle dispersion strengthening.
Lightweight materials with a density less than 3 g/cmsup.3 as potential tribo-materials for tribological applications (e.g., space tribology) are always desired. Alsub.3BCsub.3 ceramic, a kind of ...ternary material, is one of the lightweight materials. In this study, dense Alsub.3BCsub.3 ceramic is prepared via a reactive hot-pressing process in a vacuum furnace. Its tribological properties are investigated in two unlubricated conditions (one is at elevated temperature up to 700 °C in air, and another is in a vacuum chamber of back pressures from 10sup.5 Pa to 10sup.−2 Pa at room temperature) and lubricated conditions (i.e., water and ethanol as low-viscosity fluids). At 400 °C and lower temperatures in air, as well as in vacuum, the tribological property of Alsub.3BCsub.3 ceramic is poor due to the fracture of grains and formation of a mechanically mixed layer. The beneficial influence of adsorbed gas species on reducing friction is very limited. Due to the formation of lubricious tribo-oxide at 600 °C and 700 °C, the friction coefficient is reduced from ca. 0.9 at room temperature and 400 °C to ca. 0.4. In the presence of low-viscosity fluids, a high friction coefficient and wear but a polished surface are observed in water, while a low friction coefficient and wear occur in ethanol. A lubricious carbide-derived carbon (CDC) coating on top of Alsub.3BCsub.3 ceramic through high-temperature chlorination can be fabricated and the wear resistance of CDC can be improved by adjusting the chlorination parameters. The above results suggest that Alsub.3BCsub.3 ceramic is a potential lubricating material for some tribological applications.
Electroless nickel composite coatings have the potential for high-temperature tribological applications, and a combination of high wear resistance and low friction factor is one of the desirable ...solutions but still a tricky problem. The addition of self-lubricating WSsub.2 and hard Sisub.3Nsub.4 nanoparticles to the Ni-P coatings is expected to obtain good high-temperature tribological performance. In this work, Ni-P-Sisub.3Nsub.4-WSsub.2 composite coatings with various contents of WSsub.2 nanoparticles were prepared using electroless plating and subsequently annealed at 400 °C in an inert atmosphere. The tribological properties of the coatings were evaluated using a ball-on-disc wear instrument at operating temperatures from 25 to 600 °C. The microstructure, chemical composition, and surface morphology of the coatings were characterized by X-ray diffractometry (XRD), energy disperse spectroscopy (EDS), and scanning electron microscopy (SEM). Upon increasing the WSsub.2 dosage in the bath, the WSsub.2 content in the coating increased and the micro-hardness of the as-plated coating increased from 539 to 717 HV. After heat treatment, the coating underwent a crystallization process, and the hardness increased from 878 to 1094 HV. The main wear mechanism of the coating changed from adhesive wear in the as-plated state to abrasive wear in the annealed state. The annealed Ni-P-Sisub.3Nsub.4-WSsub.2 coating with a WSsub.2 dosage of 2.5 g/L in the bath exhibited excellent mechanical properties, with a hardness of 10.9 GPa, a friction coefficient of ~0.51, and a wear rate of 8.4 × 10sup.−15 msup.3Nsup.−1⋅msup.−1 at room temperature, and maintained optimal performance at high temperatures. At operating temperatures of 200, 400, and 600 °C, the form of wear was adhesive wear for coatings with a WSsub.2 dosage <1.5 g/L and abrasive wear for coatings with a WSsub.2 dosage ≥1.5 g/L. The synergism of WSsub.2 and Sisub.3Nsub.4 particles refined the grains of the Ni-P matrix in as-plated coatings and obviously reduced the friction coefficient of friction pairs in annealed coatings at all operating temperatures.
The highly exfoliated Ti.sub.3C.sub.2T.sub.x nanosheets were synthesized by selective etching of the starting material of Ti.sub.3AlC.sub.2 using 40 % concentrated HF solution at 65 °C for 5 h. The ...effect of HF treatment temperature on the exfoliation degree was investigated by characterizing the morphology and microstructure of the Ti.sub.3C.sub.2T.sub.x nanosheets using SEM, XRD, and TEM. The results showed that the exfoliation degree of Ti.sub.3C.sub.2T.sub.x was increased with increasing temperature. The role of the termination groups produced during HF treatment on the exfoliation degree was discussed. The tribological property of the prepared Ti.sub.3C.sub.2T.sub.x nanosheets as additives in PAO8 base oil was measured. The maximum reduction of friction and wear was achieved under additive concentration of 0.8 wt% for the highly exfoliated Ti.sub.3C.sub.2T.sub.x nanosheets. The different effects of Ti.sub.3C.sub.2T.sub.x additives on the average friction coefficient and wear volume were analyzed, respectively.
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