Uniting superhardness and damage-tolerance in a nanosandwich-structured Ti–B–N coating

A novel nanosandwich-structured Ti–B–N coating was prepared on a Ti–6Al–4V substrate using a double glow discharge plasma technique. This coating consists of alternating Ti(N,B) nanocrystalline layers, containing nanoscale growth twins, and amorphous TiB2–BN layers. Compared with a monolithic TiB2.06 nanocrystalline coating, the new Ti–B–N coating exhibits a marked increase in both damage resistance and hardness (i.e. ∼55 GPa). The enhanced mechanical properties were found to stem from a combination of nanostructuring and nanotwinning effects.