Achieving controllable friction of ultrafine-grained graphite HPG510 by tailoring the interfacial nanostructures

•Friction and wear of ultrafine-grained graphite HPG510 is studied in ambient air.•Ultralow friction of HPG510 is achieved by using liquid lubricant or DLC film.•The in situ formed tribolayer is analyzed to reveal the lubrication mechanism.•It provides a new pathway to extend the application range of graphite lubricants.