Tribological Performance of Textured DLC/CrN Coatings on Cemented Carbide Surfaces

The CrN serves as a buffer layer to improve interfacial adhesion between the substrate and the DLC, while the DLC layer provides high hardness, chemical inertness, and low friction characteristics. The coating system was comprehensively characterized using X-ray diffraction (XRD) to determine phase structure, Raman spectroscopy to evaluate the sp2/sp3 bonding characteristics of the DLC, and nanoindentation to assess hardness and elastic modulus.

Tribological tests were carried out using a ball-on disc configuration under two representative working conditions: low-speed/low-load (10 N, 1 m/s) and high-speed/high load (20 N, 6 m/s). Friction coefficient measurements and surface wear morphologies were analyzed under forward and reverse sliding directions. The results revealed that the combination of surface micro-texturing and DLC coating significantly enhanced the tribological performance of the WC samples.

Under low-speed and low-load conditions, the reverse Tesla-textured and coated sample (D-RT) exhibited the lowest friction coefficient of 0.069, along with the smallest wear volume of the counter ball (11.2 × 106 μm3). Conversely, under high-speed and high-load conditions, the forward Tesla-textured coated sample (D-FT) demonstrated superior wear resistance, achieving a friction coefficient as low as 0.049 and a counter ball wear volume of only 9.3 × 106 μm3.

The tribological performance is largely attributed to the high hardness and low shear strength of the DLC layer, which protects the substrate from direct contact and plastic deformation. Moreover, the micro-textures, particularly those mimicking Tesla valve geometry, introduce an asymmetric flow field and contact stress distribution, enabling directional friction control and enhanced wear mitigation. In summary, this work demonstrates a promising surface modification approach for WC-based tools by integrating directional micro-texturing with high-performance DLC coatings.