High-temperature stability of TiAlN/TiB2 multilayers grown on Al2O3 substrates using IBAD

TiAlN/TiB2 multilayers which have various modulation ratios (tTiAlN:tTiB2) ranging from 1:6 to 18:1 were synthesized on Al2O3(111) substrate by ion beam assistant deposition (IBAD). The effects of annealing on the mechanical and structural properties of the multilayers were investigated using X-ray diffractometry (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and Nanoindenter (CSM instruments). It was found that the hardness for all multilayers was higher than TiAlN or TiB2 monolayer and the highest hardness of 43 GPa was attained at tTiAlN:tTiB2 = 16:1. The multilayers show the polycrystallines of TiAlN(111) and (220) textures. The thermal stability characteristics of the multilayers were studied in vacuum furnace for 30 min at temperatures of 500 and 700 °C. Compared with as-deposited multilayers, the annealed multilayers displayed a stable hardness and elastic modulus and an increased fracture resistance. It was found that the multilayers showed good thermal stability.

► TiAlN/TiB2 multilayer is a candidate as protective coating in high temperature.
► Modulation ratio is key factor corresponding to its hardness and fracture resistance.
► Highest hardness of 43 GPa was attained at tTiAlN:tTiB2 = 16:1.
► Structure and properties kept thermal stability after annealing.