Tribological properties and microstructure of monolayer and multilayer Ta coatings prepared by magnetron sputtering

Abstract

To improve the wear resistance of medical titanium alloy, Ta coatings were prepared by magnetron sputtering method on Ti6Al4V substrates. Phase structure and surface morphology of Ta coatings were characterized by X-ray diffraction and atomic force microscope, respectively. The properties of Ta coatings, including adhesion, nano-hardness, and wear resistance, were tested using nano-scratch, nano-indentation and tribometer, respectively. The results show that both stable body-centered cubic (α-Ta) phase and metastable tetragonal phase (β-Ta) coexist in a multi-layer structure, and it shows a non-columnar feature. Interestingly, only a pure phase with columnar crystals is found in monolayer Ta coating. A body-centered cubic (α-Ta) phase is found in a monolayer prepared under the pulse power bias voltage with low deposition temperature. A pure metastable tetragonal phase (β-Ta) is prepared under the direct current bias voltage, which has the best adhesion and wear resistance compared with other Ta coatings.