Tribological behaviour and lubrication performance of hexagonal boron nitride (h-BN) as a replacement for graphite in aluminium forming

In this work the possibility of replacing graphite with h-BN in Al-forming lubricants was investigated, including the influence of h-BN powder size and concentration on its tribological performance and the aluminium's surface quality. The results of the investigation show that h-BN, as a solid lubricant, is capable of successfully replacing graphite in Al-forming processes, while at the same time maintaining a clean surface without staining. The study has shown that the tribological performance, including the friction and wear, the lubrication-film stability and the surface quality, very much depend on the powder size and the concentration. Under the investigated contact conditions, the best performance was obtained for 30-µm h-BN powder when added to the grease in a concentration between 10 and 20%.