Large-area deposition of protective (Ti,Al)N coatings onto polycarbonate.

This article focuses on the development and characterization of (Ti,Al)N protective hard coatings deposited onto polycarbonate (PC) substrates, addressing the challenges posed by the vastly different material properties of polymers and ceramics. By systematically varying pulsing parameters in a large-area sputtering process, specifically using pulsed direct current magnetron sputtering (DCMS) at a target peak power density of 0.036 kW cm⁻² and a duty cycle of 5.3%, the study achieved adherent (Ti,Al)N coatings with reduced residual tensile stress (~2.2 GPa) and confirmed adhesion via cross-cut testing. X-ray photoelectron spectroscopy revealed interfacial bonding primarily through CNₓ and (C−O)−(Ti,Al) bonds, while nanoindentation and electrochemical impedance spectroscopy demonstrated the coating’s mechanical robustness (elastic modulus ~296 GPa) and formation of a protective Ti–Al–O passivation layer under oxidative conditions. The findings highlight that controlling deposition parameters can effectively mitigate stress-induced failures and enable durable, protective coatings on soft polymer substrates like PC.