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

ZrB2/W and ZrB2/WNx multilayers with modulation periods (Lambda) 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 rnultilayers. All of ZrB2/W rnultilayers possessed higher hardness and fracture resistance than monolithic ZrB2 or W coatings. Compared with Ar+ bombardment, N+ bombardment gave a further contribution to mechanical properties of ZrB2/WNx multilayers. The maximum hardness and critical load of ZrB2/WNx coating, when A 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 ZrB2/WNx 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. (C) 2012 Elsevier B.V. All rights reserved.