Structure, mechanical and tribological properties, and oxidation resistance of TaC/a-C:H films deposited by high power impulse magnetron sputtering

TaC/a-C:H films with varying carbon content within a narrow window were deposited employing HiPIMS in the Ar/C2H2 atmosphere. The DC deposited TaC/a-C:H reference films were prepared under the same deposition parameters for comparison. Analysis and comparison of the chemical bonding state, structure, mechanical and tribological properties, and oxidation resistance of the films were conducted, with the aim of emphasizing the differences in the nanocomposite structure and properties of the films correlated to deposition conditions. It reveals that the HiPIMS deposited TaC/a-C:H films outperform the DC deposited ones, exhibiting higher hardness and toughness, lower friction coefficient and wear rate, and stronger oxidation resistance. The improved performances in HiPIMS are attributed to HiPIMS plasma, which enables (i) the volume fraction of crystalline TaC phase and amorphous carbon phase, (ii) the stoichiometric ratio and grain size of the crystalline phase, (iii) the sp(2)/sp(3) -C ratio, and (iv) the residual stress to develop in the manner that is conducive to film properties. It is demonstrated that HiPIMS plasma can be used as an effective means to modulate the chemical bonding state and nanocomposite structure of TaC/a-C:H film for achieving higher performance in terms of hard yet tough, wear and oxidation resistance.