Tribochemistry of adaptive integrated interfaces at boundary lubricated contacts

Abstract

Understanding how an adaptive integrated interface between lubricant additives and solid contacts works will enable improving the wear and friction of moving engine components. This work represents the comprehensive characterization of compositional and structural orientation at the sliding interface from the perspective of surface/interface tribochemistry. The integrated interface of a lubricant additive-solid resulting from the friction testing of Graphite-like carbon (GLC) and PVD-CrN coated rings sliding against cast iron under boundary lubrication was studied. The results indicate that in the case of the CrN/cast iron pair the antiwear and friction behavior were very strongly dependent upon lubricant. In contrast, the tribology of the GLC surface showed a much lower dependence on lubrication. In order to identify the compounds and their distribution across the interface, x-ray microanalysis phase mapping was innovatively applied and the principle of hard and soft acids and bases (HSAB) to understand the behaviour. Phase mapping clearly showed the hierarchical interface of the zinc-iron polyphosphate tribofilm for various sliding pairs and different sliding durations. This interface structure formed between lubricant additives and the sliding surfaces adapts to the sliding conditions – the term adaptive interface. The current results help explain the tribology of these sliding components in engine.

Tribological behavior of the low‐concentration boric acid and ZDDP lubricating oil mixtures

“…Furthermore, the COF reduction efficiency ( ɳ EF ) of lubricating oil mixtures versus base oil was calculated by using the Equation and COF reduction efficiency of % 1, 3, and 5 ZDDP, and boric acid mixtures were 56%, 61%, and 64%, respectively. These results suggested that an increase in the concentration of boric acid and ZDDP slightly increased the COF reduction efficiency of steady state friction regimes at boundary lubrication regime …”

Self‐healing of TiSiN/Ag coatings induced by Ag

“…Among them, TiSiN exhibits the highest hardness with up to a theoretical value of 105 GPa . However, the microcracks are often observed in ceramic coatings during service, and some of them are internal and make the coating uncompacted while the others can penetrate the whole coating and result in the exposure of the substrate. According to Farid and Bai, although Ti–6Al–4V with the TiSiN coating demonstrated a better performance in electrochemical impedance spectroscopy (EIS) experiments than the uncoated one, algae can still adhere to its surface due to the failure of the coating induced by microcracks.…”

Biolubricant production via esterification and transesterification processes: Current updates and perspectives

“…The biolubricants displayed improved and acceptable wear and lubricity behaviour than the petroleum based‐lubricant, depending on their proposed applications. Other recent applications of biolubricants prepared by the esterification and transesterification process with enhanced tribological behaviours have been reported by Hamdan et al, 172 Hassan et al, 173 Wan et al, 174 Ameen et al, 175 Pérez‐de Brito et al, 176 and Gemsprim et al 177 However, biolubricants in the preceding years underperformed in certain applications at high temperatures and highly oxidative environments, affecting their tribological performance. This is because the maximum of the produced biolubricants is obtained from vegetable sources, with some portions containing high unsaturated fatty acids exposing them rapidly to lipid oxidation.…”