Mechanical and tribological properties of Ti-Al-Ta-N/TiAl and Ti-Al-Ta-N/Ta multilayer coatings deposited by DC magnetron sputtering

The mechanical properties, microstructure, adhesion and wear behavior of a Ti0.41Al0.48Ta0.11N monolithic coating and Ti0.41Al0.48Ta0.11N/Ti0.45Al0.55 and Ti0.41Al0.48Ta0.11N/Ta multilayers were investigated. The coatings were deposited on titanium substrates by reactive DC magnetron co-sputtering. The hardness and reduced elastic modulus of the coatings were determined by nanoindentation. The multilayer coatings were found to exhibit the lower mechanical characteristics than those of the monolithic coating due to the contribution of the softer metal interlayers to their measured values. Adhesion evaluation was performed by scratch testing. The Ti0.41Al0.48Ta0.11N/Ti0.45Al0.55 multilayer was characterized by stronger adhesion to the titanium substrate than the monolithic coating, whereas the Ti0.41Al0.48Ta0.11N/Ta multilayer exhibited poorer adhesion. In contrast, both the multilayers showed improved wear resistance compared with the monolithic coating. The best wear performance was demonstrated by the Ti0.41Al0.48Ta0.11N/Ti0.45Al0.55 multilayer that was attributed to stronger bonding between the layers as well as the lower hardness of the Ti0.45Al0.55 layers, which allowed for the accommodation of a larger amount of deformation via their plastic flow.