The Effect of Substrate Bias Voltage on the Mechanical and Tribological Properties of (TiAlZrTaNb)Nx High-Entropy Nitride Coatings

We investigate TiAlZrTaNb nitride coatings deposited on Haynes 282 nickel superalloy substrates via high-power impulse magnetron sputtering (HiPIMS) under varying substrate bias voltages (0 V to −75 V). The influence of substrate bias on the microstructure, morphology, hardness, and wear resistance was systematically analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), nanoindentation, and ball-on-disk tribometry. The coatings exhibited a near equiatomic chemical composition with a face-centered cubic (FCC) crystal structure preferentially oriented along the (200) and (111) planes. Increasing the bias voltage reduced the grain size (3.65 nm to 2.84 nm) and lattice parameter (0.442 nm to 0.440 nm); meanwhile, the hardness (>45 GPa) and wear resistance were improved. The interplay between the deposition parameters and coating-substrate interactions are discussed in order to optimize HiPIMS-derived coatings for industrial applications.