A comparative study of microstructural and tribological properties of N-DLC/DLC double layer and single layer coatings deposited by DC-pulsed PACVD process

Diamond-like carbon (DLC) coatings have been attractive for their unique properties such as high wear resistance, high hardness, chemical inertness, and biocompatibility. The double layer N-DLC/DLC coating was deposited by the D.C. Pulsed Plasma Assisted Chemical Vapour Deposition (PACVD) technique on the H13 Tool Steel. The structural, mechanical, and tribological properties of the double layer coating were compared with the single layer DLC and N-DLC coatings. The tribological behavior of the coatings was evaluated by the rotational ball-on-disk tribometer and the contact profilometer. The structural changes in the coatings were investigated by Attenuated-Total Reflectance Fourier Transform Infrared (ATR-FTIR) Spectroscopy, Visible Raman Spectroscopy, and X-ray Photoelectron Spectroscopy (XPS). The N-DLC/DLC coating showed excellent wear properties compared to single layer coatings. High stability and low friction coefficient are the most important characteristics of the double layer coating. It was found that the gradient properties in the mechanical and chemical composition of the N-DLC/DLC coating improve tribological properties and adhesion to the substrate compared to single layer.