The influence of microstructure on mechanical property of polytypic TiC/WC nanomultilayers

• The condition is very critical to achieve superhardness effect for polytypic TiC/WC multilayer.
• The maximum hardness is 41.5 GPa when WC layer is 0.5 nm.
• Template effect and mutual promotion effect should contribute a great deal for achieving superhard.

TiC/WC nanomultilayers were prepared by multi-target magnetron sputtering device. The dependence of microstructure evolution and mechanical properties has been investigated. The results showed that “mutual growth effect” and “superhardness effect” were observed in the multilayers. The polytypic WC monolayer exhibited with both triclinic α-WC and cubic β-WC structure for the carbon loss in the sputtering process. When alternately deposited with TiC layers, TiC/WC nanomultilayer would grow coherently with each other when WC layer thickness was less than 1 nm. The multilayer exhibited with cubic structure, and it would achieve 41.5 GPa when WC layer was 0.5 nm. Further increasing WC layer thickness, the hardness would drop down quickly accompanied with the disruption of coherent growth structure, and the multilayers gradually turned to exhibit polytypic structure.