Employment of Micro- and Nano-WS2 Structures to Enhance the Tribological Properties of Copper Matrix Composites

Abstract

Friction and wear are responsible for around 23% of the energy consumption in transportation, manufacturing, power generation, and residential sectors. Employed components are exposed to a wide range of operational conditions, therefore a suitable material design is fundamental to decreasing tribological issues, energy consumption, costs, and environmental impact. This study aims to analyze the effect of different solid lubricants on the suitability of copper matrix composites (CuMCs) as a potential solution to reduce the depletion of sliding electrical contacts working under extreme conditions. CuMCs samples are produced by cold-pressing and sintering to merge a high electrical conductivity with the lubricant effect supplied by different species, namely tungsten disulfide micro-powder (WS2), inorganic fullerene-like (IF) tungsten disulfide nanoparticles, and graphene nanoplatelets (GNP). The crystalline structure of the pristine and composite materials is characterized via XRD. The electrical tests show a small decrease of conductivity compared to pure copper, due to the insulating effect of WS2; however, the measured values are still adequate for conduction purposes. Micro-scratch and wear tests highlight the positive effect of the combination of WS2 structures and GNP. The friction coefficient reduction leads to the possibility of extending the lifetime of the components.

Investigation of second phase concentration effects on tribological and electrical properties of Cu–WS2 composites

“…The prepared composites reveal a hydrophobic behavior, with values ranging from 108.4±6.8° of Cu-25WS2 to 131.0±1.8° of Cu-5WS2. This last value slightly exceeds the one measured for benchmark Cu-10WS2 (130.0±3.4° [26]). Except for Cu-25WS2, the combination of the copper matrix with tungsten disulfide tends to accentuate the hydrophobicity of pure copper, previously investigated by our research group (OCA of 116.4±5.2° [26]).…”

“…This last value slightly exceeds the one measured for benchmark Cu-10WS2 (130.0±3.4° [26]). Except for Cu-25WS2, the combination of the copper matrix with tungsten disulfide tends to accentuate the hydrophobicity of pure copper, previously investigated by our research group (OCA of 116.4±5.2° [26]). However, the addition of larger contents of tungsten disulfide reduces the static contact angle values, hence slightly enhancing the wettability of the composites, likely due to the hydrophilicity of virgin WS2 powders [41].…”

“…This work aspires to investigate the effects of a fundamental aspect of the preparation of selflubricating Cu-WS2 tablets, namely the tungsten disulfide content. From previous studies of our research group [26], promising results have been obtained for a 10 wt %-concentration of WS2.…”

“…The samples have been denominated Cu-XWS2, in which X represents the lubricant mass content. Furthermore, the promising composite with 10 wt %-content of WS2, previously investigated by our research group [26], has been considered as a benchmark and subjected to additional analyses to perform a complete comparison and to better understand the effects of the second phase content on the features of copper matrix composites. Due to the commonality of the raw materials batches and to be consistent with the above-mentioned designation, the benchmark sample has been recognized as Cu-10WS2.…”

Physico-Mechanical Properties of Metal Matrix Self-Lubricating Composites Reinforced with Traditional and Nanometric Particles

“…The advance in manipulating 2D-structured materials led to their employment for tribological applications. Nanostructured materials exhibit peculiar properties, improving performances and satisfying more challenging requirements [9][10][11]. One of the most remarkable nanostructured materials developed in the last decades is graphene.…”