Anti-oxidation mechanism and interfacial chemistry of BN@CaCO3-SiO2 microcapsule-added sodium borate melt on the sliding steel surfaces at elevated temperatures
Publication Name
Applied Surface Science
Abstract
This study reports the chemistry underpinning the superior anti-oxidation and lubrication of the BN@CaCO3-SiO2 microcapsule-added sodium borate melt at 930 °C by surface-interface tailoring. Under static oxidation at 930 °C, sodium borate reacts to the microcapsule's shell that generates the sodium-calcium borosilicate melt and releases the h-BN nanosheets. Interfacial characterizations reveal a negligible corrosion attack and superior anti-oxidation of the sodium-calcium borosilicate compared to sodium borate (by ~ 86%) which is due to the weak mobility of sodium in the melt network. Under sliding conditions at 930 °C, friction modifies profoundly the interfacial reactivity of the sodium-calcium borosilicate melt toward the oxide surfaces. An intermixing effect and the friction-induced heat accelerates the high-temperature reactions between the melt and the spinel oxides on the sliding surfaces that result in the formation of the plate-like non-layered M-type CaCrxFe12-xO19 hexaferrite. A synergy between the h-BN nanosheets, the grain-refinement of the sliding surfaces, and the intercalation of the M-type hexaferrite at the sliding interfaces contribute to a superior friction reduction (by ~ 70%) compared to sodium borate melt under boundary conditions with high contact pressures. These findings highlight a potential strategy for achieving excellent lubricity, superior anti-oxidation, and reduced corrosion from the melt lubricants at high temperatures.
Open Access Status
This publication is not available as open access
Volume
566
Article Number
150556
Funding Number
LE 200100047
Funding Sponsor
Australian Research Council