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Carbon fiber reinforced polyether ether ketone (CF/PEEK) composites are widely used as tribo‐materials in the aerospace and automotive industry. To amplify the industrial utilization of extrusion‐based additive manufacturing fused deposition modeling in fabricating CF/PEEK tribo‐composites, the composites' microstructure–property relationship was studied with respect to carbon fiber content varying between 5 wt% and 30 wt%. This revealed that the incorporation of carbon fibers helped enhance the mechanical strength of PEEK greatly with an optimal content of 5 wt%, at which the composite material exhibited the highest crystallinity as well as the best mechanical performance. Tribological tests indicated that CF/PEEK composites were more suitable for high speed and heavy load conditions especially for 20 wt% CF/PEEK, which was associated with the establishment of high quality transfer films covered on counter steel surfaces. The present work provides a simple and low cost way of fabricating high performance PEEK composites used as tribo‐materials. © 2024 Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]

The orientation of fibers in polymer matrix plays a crucial role in governing the performance of composites including friction and wear. In the present work, the effect of fiber orientation on tribological behavior of 3D printed short carbon fiber reinforced PEEK composites (CF/PEEK) was studied by two series of tribo‐tests, namely macro‐scale continuous sliding and micro‐scale multiple scratching. Fiber orientations studied included parallel, tilted and anti‐parallel relative to the sliding direction in both macro sliding and micro scratching. It was revealed that the effect of fiber orientation showed strong dependence on applied loads. In most cases, lower wear were obtained when the fiber orientation was tilted rather than parallel or anti‐parallel in macro continuous sliding. With tilted orientation, the composite also exhibited the best scratching behavior except for that at the lowest normal load. To reveal the mechanisms behind this orientation effects, the composite's worn surface, as well as those of the counter rings, were characterized. Findings of the present work indicates that scratching tests can help understand the macro sliding mechanisms and appropriate fiber orientation is beneficial in improving the tribological properties of polymer composites, which can be realized through 3D printing. Highlights: PEEK composites filled with highly oriented carbon fibers were manufactured by fused deposition modeling (FDM).Tribological anisotropy was studied through macro sliding and micro scratching measurements with respect to carbon fiber orientation.The coupling mechanism of load and fiber orientation was discussed in influencing the composites' friction and wear properties. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to evaluate carbon spheres as a green lubricant additive in 5W30 engine oil to reduce friction and wear. Carbon spheres with a diameter of ∼400 nm are synthesized from glucose by using a hydrothermal process. Lubrication is studied using a ball-on-disk tribometer by measuring the friction coefficient and wear in the boundary lubrication regimes. The worn surfaces were analyzed by Raman spectroscopy. Carbon spheres are found to be stably dispersed at 0.5 wt% concentration in base oil. The experiments revealed that carbon spheres are effective in reducing both friction and wear when lubricating by using base oil. Raman results show that the enhanced tribological performance is owing to a carbon-rich boundary film, the formation of which is attributed to the deposit of carbon particles during the sliding process. [ABSTRACT FROM AUTHOR]