Comparison in microstructure and mechanical properties of nanocomposite CrWN and nanolayered CrN/WN coatings

Chromium–tungsten nitride (CrWN) and chromium nitride (CrN)/tungsten nitride (WN) multilayer coatings were fabricated by rf magnetron-reactive sputtering technique. The CrWN coating was deposited with dual gun cosputtering apparatus, while the CrN/WN coatings were manufactured by sequential CrN and WN sputtering to exhibit an alternating nanolayered feature. The microstructure of the nanocomposite and nanolayered coatings was evaluated by both scanning and transmission electron microscopy. The bilayer period of the multilayer was controlled ranging from 10 to 24 nm, with the average thickness of single nitride layer ranging from 5 to 12 nm. The nanolayered CrN/WN coatings exhibited a higher hardness of approximately 30 GPa, which was superior to that of the nanocomposite CrWN coating. The nanolayered structure which confined the grains of the nitrides in the nano range was beneficial to the enhancement of the hardness in the nanolayered coating.