Electrochemical characterization of Cr/CrN/B4C/B-C-N films deposited by magnetron sputtering under mixed Ar-Ne atmospheres

B-C-N coatings have the potential to combine the properties of B4C, BN, CNx, and carbon structures, resulting in coatings with high hardness, low friction coefficient, high wear resistance, and high corrosion resistance, making them highly attractive for many applications as protective coatings. In this investigation, the impact of the Ar:Ne flow rate ratio used in the deposition process on the properties of Cr/CrN/B4C/B-C-N films was analyzed. The films were deposited by magnetron sputtering onto AISI M2 steel and silicon wafer substrates. The study focused on analyzing the influence of Ne addition to the working atmosphere on the bonding structure, chemical composition, and electrochemical behavior of the films. Scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) techniques, Fourier transform infrared (FTIR) spectroscopy, and Xray photoelectron spectroscopy (XPS) were employed to determine the morphology, roughness, crystalline structure, BN phase fractions, atomic composition, and bonding states of the films. XRD analysis revealed that the B4C/B-C-N layers had an amorphous structure, while FTIR and XPS identified the presence of sp2 B-N, C=C, C-N, C=N, and B-O bonds within the films. Additionally, XPS studies demonstrated that higher Ne flow rate fractions (Ne70) increased nitrogen and boron content and reduced oxygen and carbon fractions, indicating enhanced nitrogen incorporation. Electrochemical tests were conducted on all samples and the uncoated metallic substrate in a 3.5 wt % NaCl solution as the electrolyte. These tests included open-circuit potential (OCP), electrochemical impedance spectroscopy (EIS), and potentiodynamic polarization (PD) measurements. The results showed that the Cr/CrN/B4C/B-C-N films deposited on AISI M2 steel exhibited superior corrosion resistance compared to the uncoated AISI M2 substrate. Notably, films deposited at higher Ne flow rate fractions exhibited 5.0-fold improved corrosion protection, attributed to lower porosity and denser microstructure.