Influence of bilayer periods on structural and mechanical properties of ZrC/ZrB_2 superlattice coatings

摘要

ZrC/ZrB_2 multilayered coatings with bilayer periods ranging from 4.4 to 35.5 nm were synthesized by r.f. magnetron sputtering. X-ray diffraction, scanning electron microscopy and nanoindention were employed to investigate the microstructure and mechanical properties of the nanoscale multilayers. The results indicated that all coatings had the clear multilayered structure with mixed ZrB_2(0 0 1), ZrB_2(0 0 2) and ZrC(1 1 1) preferred orientations. The maximum hardness (41.7 GPa) was observed in the multilayer with 27.5-nm thick period, which is about 25% higher than the rule-of-mixture value of the monolithic ZrC and ZrB_2 coatings. It also exhibited the best adhesion. Its critical load was over 70 mN. While through insert ZrB_2 into ZrC layer periodically, higher residual stress built in ZrC layer can be released.