The influence of N+ beam bombardment and deposition temperature on the growth of ZrB2/WNx nanomultilayers

ZrB2, WNx and ZrB2/WNx multilayered coatings were synthesized by ion beam assisted deposition at room temperature and 430 °C. Extensive measurements were taken to investigate the influences of N+ bombarding energy and deposition temperature on the microstructure and mechanical properties of the multilayers with different modulation periods. A well-defined composition modulation and layer structure with a mixed polycrystalline was found in the multilayers by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Nano indenter analysis indicated that almost all the multilayers synthesized under N+ bombardment at different energies possessed higher hardness and elastic modulus than the rule-of-mixtures value of monolithic ZrB2 and WNx coatings. The highest hardness and critical fracture load were over 30 GPa and 75.7 mN at 200 eV. Deposition temperature also contributed to mechanical properties. At a constant N+ bombarding energy of 200 eV, a deposition temperature of 430 °C produced a maximum hardness value of 36.6 GPa for the ZrB2/WNx multilayer with an estimated modulation period of 5.2 nm. This hardest multilayer also showed the improved elastic modulus and residual stress.