Enhancing Micro-Hardness of Mild Steel by Dielectric Barrier Discharge Plasma Jet Enhanced Chemical Vapor Deposition of TiO2

Low and medium-carbon steels, though economical, are more prone to corrosion and wear than stainless steels. Various surface modification techniques, including carburizing, laser hardening, electroplating, thermal spraying, and physical/chemical vapor deposition (PVD/CVD), are commonly applied to enhance their hardness, wear resistance, and corrosion resistance. Plasma-enhanced chemical vapor deposition (PECVD) is particularly effective for depositing thin ceramic films onto metal substrates like carbon steels, providing improved hardness and thermal/corrosion protection. Unlike conventional PVD/CVD, which requires high temperatures, complex vacuum setups, and has limited deposition rates, PECVD can operate at atmospheric pressure and offers benefits like lower temperature requirements, higher deposition rates, and reduced energy consumption. In this study, dielectric barrier discharge (DBD) plasma jet-enhanced CVD is used to deposit a TiO2 coating on mild steel to improve its wear and corrosion resistance. Liquid tetraisopropyl orthotitanate (TIOT) is used as the precursor, yielding a TiO2 layer approximately 11 microns thick. Scanning Electron Microscopy (SEM) and optical microscopy are used to analyze coating morphology, thickness, and roughness. X-ray Photoelectron Spectroscopy (XPS) confirms the chemical composition of the coating. A subsequent annealing process with varying temperatures is conducted to evaluate its impact on the crystallinity and micro-hardness of the TiO2 layer. Experimental results show that the DBD plasma jet-enhanced CVD, combined with annealing, significantly enhances the micro-hardness of mild steel, allowing high wear and corrosion resistance. This technique shows promise as a rapid, low-energy, and ambient-pressure method for durable coatings. Future studies could further optimize parameters such as precursor flow rate and input power, explore alternative precursors, and apply quicker post-treatments like laser heat treatment to expand the applications of the proposed approach.