Modulation of structure and corrosion behavior of Si-DLC coatings on AZ31 by applying a self-source bias

Abstract

The Si-DLC coating was fabricated on AZ31 via a dual system consisting of a self-source bias and a meshed plasma immersion deposition, where the incident ion energy can be modulated by the self-source bias. The structure was characterized using field emission scanning electron microscope, transmission electron microscope, Raman spectroscopy, and Fourier transform infrared spectroscopy. The corrosion behavior was evaluated using an electrochemical workstation. The utilization of the bias significantly densifies the coating structure, producing a nano-sized SiC phase and elevating its corrosion resistance. Notably, the −500 V bias coating exhibits superior short-term corrosion resistance. Interestingly, the high-energy ion bombardment produced by the high bias induces carbon diffusion in the coating, leading to the formation of a nano-ceramic TiC interface, which further enhances the corrosion resistance of the Si-DLC coating. Moreover, the increase in bias is accompanied by a decrease in surface porosity, hydrogen content, and sp2/sp3 ratio. In addition, the mechanisms involved in the formation of the TiC nano-interface and the corrosion resistance of the coating are analyzed and explained. A modulated approach to enhance the corrosion resistance of Si-DLC coatings and provide protection against magnesium alloys is achieved by dense structures resulting from high-energy ion bombardment.