Mechanical and anti-corrosion behaviour of ZrNxOy films deposited by Reactive High-Power Impulse Magnetron Sputtering for maritime applications

The maritime industry is one of the most prominent players in globalisation. Corrosion, wear, and biofouling are common problems in sea-chest gratings, constantly exposed to seawater. PVD technologies could avoid these problems by supplying environmentally friendly multifunctional solutions. This work developed zirconium oxynitrides films through high-power impulse magnetron sputtering technology in a reactive atmosphere (R-HiPIMS), using two kinds of oxygen inlet flow regimes: pulsed and steady. SEM-EDS, AFM and XRD assessed the coatings' physical and structural properties. Nanoindentation and scratch tests established the mechanical properties and film adhesion. Potentiodynamic polarisation (PP) and electrochemical impedance spectroscopy (EIS) determined the corrosion resistance of the coatings using saline solution (3.5 % wt. NaCl) until 168 h of exposure. The deposition conditions promoted the featureless growth profile with high densification in the films. The oxygen pulses during deposition promoted a multilayered stack growth with poor and rich oxidised layers, which showed a mixed-phase microstructure from ZrN to ZrO2 and some intermediate phases. The film growth directly influenced the hardness in multilayered films and mixed phases in the monolithic ones. Films adhesion improved with oxygen inclusion. Corrosion tests disclosed that the film densification ruled the corrosion resistance. Implementing HiPIMS technology could contribute to achieving sea-chest gratings with higher corrosion resistance, reducing maritime industry costs.