Tribochemical Interactions between Graphene and ZDDP in Friction Tests for Uncoated and W-DLC-Coated HS6-5-2C Steel

Abstract

If a lubricant contains structures capable of conducting energy, reactions involving zinc dialkyldithiophosphate (ZDDP) may take place both very close to and away from the solid surfaces, with this indicating that ZDDP can be a highly effective anti-wear (AW) additive. The central thesis of this article is that the tribocatalytic effect is observed only when the energy emitted by the solids is transmitted by ordered molecular structures present in the lubricant, e.g., graphene. The friction tests were carried out for 100Cr6 steel balls in a sliding contact with uncoated or W-DLC-coated HS6-5-2C steel discs in the presence of polyalphaolefin 8 (PAO 8) as the lubricant, which was enhanced with graphene and/or ZDDP. There is sufficient evidence of the interactions occurring between ZDDP and graphene and their effects on the tribological performance of the system. It was also found that the higher the concentration of zinc in the wear area, the lower the wear. This was probably due to the energy transfer resulting from the catalytic decomposition of ZDDP molecules. Graphene, playing the role of the catalyst, contributed to that energy transfer.

Facile formulation of graphene oxide modified commercial polyurea grease and its enhanced tribological capability under extremely high contact stress

“…Nevertheless, when the concentration of GO in PU grease exceeds 2.0%, the friction coefficient gets worse and tends to be similar to that of PU in Figure 4A. Also, as compared with the frictional response of steel pair lubricated with PU grease, GO modified PU greases display the relatively stable friction between the tribosurfaces, which is essentially due to the excellent lipophilicity, dispersibility and stability of GO 23 …”

“…Also, as compared with the frictional response of steel pair lubricated with PU grease, GO modified PU greases display the relatively stable friction between the tribosurfaces, which is essentially due to the excellent lipophilicity, dispersibility and stability of GO. 23 The specific wear rate of steel disc in Figure 4B well reveals that, mixing graphene oxide into PU grease yields a considerable decrease in material loss when the concentration of GO lies in the proper range of 1.5 $ 2.0 wt.%, thus the presence of GO in PU grease greatly contributes to wear prevention between the steel-to-steel contact. However, as the concentration of GO exceeds 2%, a distinct enlarging wear rate occurs in Figure 4B.…”

Characterization and Properties of Diamond-Like Carbon Coatings

“…DLC coatings have aroused great scientific and industrial interest since the beginning of the 70s due to their very good mechanical, physical [1], tribological and anti-corrosion properties [2]. The coatings have a very smooth surface [3][4][5], high hardness [1,[3][4][5][6], low friction coefficient, high wear resistance [1,3,4,7,8], good thermal conductivity, high transparency [1,5], good chemical inertness [1,[4][5][6] and biocompatibility [1,4,7,9].…”

Graphene-Based Materials, Their Composites, and Potential Applications

“…Two articles deal with the effect of graphene nanoplatelets over the friction and wear properties of materials; both are key characteristics from the industrial point of view. The work of Omrani et al [ 13 ] highlights the effect of multilayer graphene sheets as a solid lubricant for Al and Al/alumina composites, whereas the article by Kowalczyk et al focuses on the interactions between graphene and a common lubricant, ZDDP (zinc dialkyldithiophosphate), for reducing friction and wear in both bare and DLC-coated steels [ 14 ].…”

“… A schematic diagram of the graphene composites spectrum and their potential uses along with representative examples of materials and uses from the articles included in this Special Issue. ( a ) A schematic of the applications of graphene-based composites in Li-ion battery electrodes described in [ 11 ]; ( b ) a high annular dark field (HAADF) micrograph of an Al/2GNP/1Al 2 O 3 composite [ 13 ]; ( c ) an isometric view of a PAO8/ZDDP/graphene W-DLC surface after a ball-on-disc test [ 14 ]; ( d ) CVD graphene-coated γ-Al 2 O 3 nanofiber [ 15 ]; ( e ) reinforced 3D-printed MWCNT and rGO/Al 2 O 3 scaffolds [ 16 ]; ( f ) a schematic of an experimental setup for gas-sensing applications [ 10 ]; ( g ) a schematic diagram of sulfamethoxazole detection by silica-coated GQDs [ 12 ]. …”