Assessment of the tribocorrosion performance of a (TiZrNbTaMo)C refractory high entropy alloy carbide coating in a marine environment

To improve the tribocorrosion performance of mechanical components applied in marine environments, a (TiZrNbTaMo)C refractory high entropy alloy carbide (RHEAC) coating was deposited using a sputtering deposition technique onto a commercial purity Ti substrate. The as-synthesized RHEAC coating, with an average thickness of approximately 22 µm, exhibited a single-phase face-centered cubic (FCC) crystal structure, composed of equiaxed grains with an average diameter of approximately 9 nm. The tribocorrosion performance of the RHEAC coating was investigated by both open circuit potential (OCP) and potentiodynamic polarization measurements in 3.5 wt% NaCl solution. Under both static corrosion and tribocorrosion conditions, the RHEAC coating showed higher OCP values relative to the uncoated substrate. Similarly, the potentiodynamic polarization measurements revealed that the RHEAC coating exhibited more noble corrosion potential values and a lower corrosion current density under both static and tribocorrosion conditions, in comparison with uncoated Ti. After application of the RHEAC coating, the specific wear rate of commercially pure Ti was lowered by two orders of magnitude under conditions of both tribocorrosion and dry sliding wear. Moreover, Mott-Schottky and point of zero charge (PZC) measurements suggested that the passive film present on the RHEAC coating exhibited a smaller donor density as well as a higher capacity to impede Cl− ions adsorption than the passive film grown on uncoated substrate.