Effect of substrate bias on the structure and properties of multi-element (AlCrTaTiZr)N coatings

Abstract

Multi-element (AlCrTaTiZr)N coatings are prepared by reactive RF magnetron sputtering. The influence of substrate bias (0 to −200 V) on the deposition rate, composition, structure and mechanical properties of these coatings is investigated. A reduction in both deposition rate and Al concentration is observed with increasing substrate bias. The grounded substrate is found to possess a columnar structure. The columnar structure is not so apparent in the denser coatings deposited at an applied substrate bias of −150 V. Furthermore, a minimum in coating roughness is found to occur at the intermediate substrate bias of −100 V. All the (AlCrTaTiZr)N coatings appear to have a single FCC structure from XRD analysis. Furthermore, it is determined from XRD that there is an increase in both (111) peak intensity and grain size, and a decrease in the lattice strain, for increasing substrate bias. The residual stress, hardness, elastic modulus and toughness of the coatings are found to be greatly enhanced by the substrate bias. The highest hardness and elastic modulus of approximately 36 Gpa and 360 GPa, respectively, were obtained at a substrate bias of −150 V.