Influence of modulation periods and modulation ratios on the structure and mechanical properties of nanoscale TiAlN/TiB2 multilayers prepared by IBAD

Alternate hard TiAlN/TiB2 multilayers with different modulation periods (Λ) ranging from 0.6 to 27 nm and modulation ratios (tTiAlN:tTiB2) ranging from 8:1 to 25:1 were prepared using an ion beam assisted deposition (IBAD) system. The effect of Λ and tTiAlN:tTiB2 on the hardness, elastic modulus, residual stress, and fracture resistance were investigated using various characterization techniques. All multilayers with clear interfaces displayed higher hardness than individual TiAlN and TiB2 layers. The maximum hardness of 35 GPa and critical load of 84 mN were obtained for the multilayer with a Λ of 2.2–8.8 nm and tTiAlN:tTiB2 of 8:1. Strong TiAlN (111) crystallographic texture as well as multilayer structure is thought to be be responsible for the increasing hardness of the TiAlN/TiB2 multilayers.

► TiAlN/TiB2 multilayer has potential on quality in protective coatings.
► Modulation period and ratio are related to its properties.
► A critical modulation period and ratio correspond to the hardest multilayer.