Formation of Single-Phase Ti–Au Intermetallic Coatings via Au Deposition and Annealing-Induced Diffusion: Microstructure and Electrochemical Performance

Ti–Au intermetallic compound (IMC) coatings have attracted considerable interest for biomedical devices and corrosion-protective surfaces owing to their excellent corrosion resistance, hardness, and biocompatibility. Although magnetron sputtering is widely used for high-performance functional coatings, conventional co-sputtering strategies tend to induce undesired secondary-phase formation in Ti–Au coatings, impairing phase stability and coating performance. In this work, Ti–Au IMC coatings were fabricated through a sequential Au-deposition/diffusion-annealing route, and the effects of annealing temperature and holding time on phase formation, phase selection, and microstructural evolution were systematically examined. Diffusion annealing produced a bilayered coating, with Ti3Au preferentially formed in the inner layer, while the outer layer evolved successively from TiAu2 to TiAu and then to Ti3Au as diffusion proceeded. Under sufficient diffusion conditions, the coating was converted into a single-phase Ti3Au intermetallic layer. Despite the limited durability of Ti–Au IMC coatings under the harsh PEMFC environment, electrochemical measurements in corrosive human body environments confirmed the corrosion resistance of the Ti–Au IMC coatings. The diffusion-mediated route via magnetron sputtering with annealing offers a practical means of tailoring Ti–Au IMC coatings for corrosion-stable biomedical and protective applications.