STRUCTURES AND MECHANICAL PROPERTIES OF MODULATED ZrB2/W AND ZrB2/WNx NANOMULTILAYERS

摘要

ZrB2,W,WNx coatings and ZrB2/W, ZrB2/WNx multilayered coatings have been synthesized by ion beam assisted deposition at room temperature. X-ray diffraction (XRD), XP-2 surface profiler, scanning electron microscopy (SEM) and nano indenter were employed to investigate the influence of modulation periods and N+ beam bombardment on microstructure and mechanical properties of the coatings. The low-angle XRD patterns and cross-sectional SEM indicate a well-defined composition modulation and layer structure of the multilayers. The multilayers with modulation periods ranging from 9 to 16 nm without N+ bombardment possessed higher hardness and elastic modulus than the rule-of-mixtures value of monolithic ZrB2 and W coatings. The highest hardness was 24 GPa. N+ bombardment to growing multilayers gave a significant contribution to mechanical property enhancement. When modulation period is 9.6 nm, ZrB2/WNx multilayer with 200 eV N+ bombardment reveals the highest hardness (30.2 GPa) and elastic modulus. This hardest multilayer also showed the improved residual stress and fracture resistance.