Preparation and characterization of superhard TiC/Mo multilayers

Nanometer scale TiC/Mo multilayers have been prepared by ion beam assisted deposition (IBAD) at nearly ambient temperature. The modulation wavelength was in the range of 2 nm to 14 nm and the individual layer thickness was maintained to be equal. Two series (series A and series B) were prepared which were bombarded with different bombarding energy (0 eV and 50 eV) in order to investigate the bombardment effect on the nano-hardness of the multilayers. Low angle X-ray diffraction (LXRD) was used to analyzed the layered structure of multilayers. Mechanical properties of these multilayers were thoroughly studied using a nanoindentation facility. The nanohardness showed a strong dependence on the sharpness of the interlayer and the modulation wavelength. It was found that the multilayer hardness was greater than the volume weighted mean of the component hardness. With the modulation wavelength adjusted, the multilayer can be even harder than its hard component (TiC). A maximum hardness of 47.62 GPa, about 1.5 times larger than that of the TiC values, was found at λ = 8 nm multilayer deposited without ion beam bombardment. It was also found that the films without ion bombardment were much harder than those bombarded by 50 eV Ar^PLU ion beam.