Tribochemical insights into the carbon film formation induced by metallic species derived from layered double hydroxide nanoadditives

•Five carbonate LDHs reduce wear loss and friction by 90% and 20%, respectively.•Catalytic cobalt species induce the formation of thick carbon film.•Various carbon species are identified by EELS at different regions of interest.•Cobalt diffusion enhances bonding at the tribofilm-steel interfaces.•Nanomechanical properties are evaluated by nanoindentation and nanoscratch.