Manufacture, microstructure and mechanical properties of CrWN and CrN/WN nanolayered coatings

Chromium nitride and tungsten nitride coatings were fabricated in sequence to form a CrN/WN nanolayered coating by rf reactive magnetron sputtering technique with a dual-gun system. The CrWN coating was also manufactured for comparison. The bilayer period of the nanolayered CrN/WN coating were controlled at 10 and 24 nm. Periodic feature of elemental distribution of the nanolayered coatings was revealed by the Auger electron spectroscopy depth profiling analysis. The phase identification results indicated that the composite CrWN coating was composed of CrN phase with solid-solution of W, while CrN and amorphous/nanocrystalline WN and W2N phases was observed in the nanolayered CrN/WN coatings. The CrN/WN nanolayered microstructure was evaluated by scanning and transmission electron microscopy. Nanoindentation technique was employed to evaluate the mechanical properties, including hardness and Young's modulus. The nanolayered CrN/WN coatings exhibited a high hardness around 30 GPa, which was superior to that of the CrWN coating. The nanolayered structure with confined grains of the nitrides in the nano range was beneficial to the enhancement of the mechanical performance for the multilayer coating.