Tailoring the performance of DLC coatings through interlayer engineering

Diamond-like carbon (DLC) coatings have been widely studied for their exceptional hardness, low friction, and excellent wear and corrosion resistance, making them highly attractive for biomedical and industrial applications. However, their practical implementation is often hindered by internal stress and poor adhesion to metallic substrates. In this study, the effect of interlayers including plasma nitriding (PN), zirconium nitride (ZrN), and tantalum nitride (TaN) on the microstructure, wear behavior, and corrosion resistance of DLC coatings was investigated. FESEM images revealed a high density and uniformity of the DLC coatings in all three samples, with crack-free and pore-free surfaces. AFM analysis indicated that the ZrN + DLC and TaN + DLC samples, with surface roughness values of 3.42 nm and 3.31 nm respectively, exhibited smoother surfaces compared to the PN + DLC sample, which had a roughness of 42.34 nm. Wear testing showed that the TaN + DLC sample exhibited the lowest weight loss (8 mg) and wear rate (0.001901 mm³/N·m). Moreover, impedance curves indicated the highest corrosion resistance in the TaN + DLC sample. These findings demonstrate that the incorporation of ZrN and TaN interlayers significantly enhances the surface characteristics, particularly surface roughness and structural uniformity, along with the wear and corrosion resistance of DLC coatings.