Example: Walk on the seaside (Courtesy Jörg Pattscheider, Empa)
The foot sinks in dry sand.
Not in the wet sand. Because the spaces between the sand grains are filled with water. The surface has a higher resistance, so it is harder. In the nanocomposite coatings the nanocrystalline grains (AlTiN, AlCrN, etc.) are the hard grains. The tough Si3N4 is the binder.