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

摘要

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 30GPa and 75.7mN at 200eV. Deposition temperature also contributed to mechanical properties. At a constant N+ bombarding energy of 200eV, a deposition temperature of 430°C produced a maximum hardness value of 36.6GPa for the ZrB2/WNx multilayer with an estimated modulation period of 5.2nm. This hardest multilayer also showed the improved elastic modulus and residual stress.