Ar+ or N+ bombardment induced the microstructure and mechanical properties of ZrB2/W and ZrB2/WNx superlattice coatings prepared by IBAD

Abstract ZrB 2 /W and ZrB 2 /WN x multilayers with modulation periods ( Λ ) ranging from 3 to 12.5 nm were prepared under Ar + or N + bombardment by ion beam assisted deposition. Extensive measurements were employed to investigate the influences of different ion bombardments and modulation periods on microstructure and mechanical properties of the multilayers. A well-defined composition modulation and layer structure with a mixed polycrystalline was proven in the multilayers. All of ZrB 2 /W multilayers possessed higher hardness and fracture resistance than monolithic ZrB 2 or W coatings. Compared with Ar + bombardment, N + bombardment gave a further contribution to mechanical properties of ZrB 2 /WN x multilayers. The maximum hardness and critical load of ZrB 2 /WN x coating, when Λ was 9.6 nm and N + bombarding energy was 200 eV, were up to 30.2 GPa and 65.5 mN, respectively. This hardest multilayer also showed the improved residual stress. These enhanced effects in ZrB 2 /WN x coatings were likely the result of the resistance to dislocation glide and columnar grain growth across interface as well as nanoscale strain optimization as the evolution of layer crystalline.