Synergistic tribology behaviours of triethanolamine borate and TiO2/hBN nanoadditives in novel hybrid water-based nanolubricants

Excessive friction and wear during sliding remain critical challenges in mechanical systems, and the formation of the tribo-oxide layer during this process significantly influence surface quality. This study firstly investigates triethanolamine borate (TEA-B) as an eco-friendly chemical additive in TiO 2 /hBN hybrid water-based nanolubricants to further improve tribological performance. Tribotests with ball-on-disc configuration were conducted under dry, water, and nanolubricant conditions containing TEA-B concentrations from 0 to 5 wt%. The coefficient of friction (COF), wear rate, and wear scar were systematically evaluated, also the morphologies and compositions of tribo-oxide layer analysed by SEM, XPS, and Raman spectroscopy. The optimum condition shows that the utilisation of 5 wt% TEA-B significantly reduced the COF to 0.088 and decreased the wear rate by 87.47% compared with dry condition. XPS and Raman analyses confirmed that TEA-B effectively suppressed the oxidation of Fe 2+ to Fe 3+ , thereby stabilising the tribo-oxide layer with higher fractions of ductile Fe 3 O 4 and FeO rather than brittle Fe 2 O 3 . This chemically modified tribo-oxide layer, combined with the rolling and mending effects of TiO 2 /hBN nanoadditives, facilitated the formation of a stable and protective tribofilm. These findings provide new insights into the synergistic lubrication mechanisms of nanolubricants, and highlight the potential of TEA-B-enhanced formulations as environmentally friendly additive for advanced tribological applications.