Abstract
The increasing demand for low-viscosity engine oil has underscored the role of zinc dialkyldithiophosphates (ZDDP) as a conventional anti-wear and antioxidant additive. It is essential to investigate the influence of modern additives such as cyclopropanecarboxylic acid (CPCa) and Ni nanoparticles on the tribological performance of ZDDP for practical commercial oil application. According to the experimental results, Ni nanoparticles formed a protective film that exhibited a synergistic effect with ZDDP. A significantly higher concentration of sulphur in the tribofilm was detected compared to ZDDP by itself, which was responsible for a 27.6% lower wear loss. Meanwhile, a competitive effect between CPCa and ZDDP resulted in a dramatic increase in friction and unstable anti-wear performance. This was demonstrated by a localized formation of the ZDDP tribofilm on the wear surfaces after the friction test. These results have highlighted the synergistic and competitive effects of emerging additives (CPCa and Ni nanoparticles) in the ZDDP tribofilm formation between the sliding steel contacts. This further suggests a new approach to increase the efficiency of ZDDP’s tribological performance at cold start-up processes.
Highlights
The disc wear track profile of the PAO oil shown in Figure 2a showed the most obvious wear scar with no additive
It can be concluded that the cyclopropanecarboxylic acid (CPCa) additive in two experiments resulted in a carbonfilm formation with a significantly high graphitic degree that could deliver remarkable anti-friction property [35]
This study has investigated the influence of CPCa and Ni nanoparticles on the tribological performance of zinc dialkyldithiophosphate (ZDDP) in PAO oil ambient
Summary
Due to the increasing demand for low-viscosity engine oils [1], zinc dialkyldithiophosphate (ZDDP) as a conventional lubricating additive has been widely used. There is a need for ZDDP to reduce the friction and wear of moving parts to improve engine efficiency [2]. ZDDP decomposes and reacts with the oxide layer of the sliding substrate, forming the pad-like structure tribofilm. This tribolayer acts as a cushion preventing wear and inhibits the oxidation process on the sliding surface [4,5]. The reduction of ZDDP usage is currently encouraged because it produces harmful emissions of
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