Effect of WC thickness on the microstructure and properties of WC-C/DLC coated 304 steel

• A PVD/CVD hybrid process deposited a WC-C/DLC multilayer on 304 steel, enhancing WC-DLC adhesion. • WC-C interlayer thickness had minimal impact on the roughness and tribology of multilayer-coated 304 steel. • The hardness and elastic modulus of WC-C/DLC coated samples reflected the combined effects of both WC-C and DLC coatings. A tungsten carbide (WC) layer on 304 stainless steel enhances the hardness, wear resistance, and low friction of the diamond-like carbon (DLC) coating, making it suitable for harsh environments. However, high residual stress and low toughness in WC/DLC coatings cause early failures due to delamination and fractures, limiting their practical use. This study employs a hybrid PVD and CVD process to enhance the adhesion between the WC layer and DLC coating, investigating how variations in WC composition and thickness, with a constant DLC thickness, affect the structure and properties of the multilayer coated steels. Results indicate that the WC surface formed an amorphous carbon (WC-C) layer, boosted DLC adhesion to steel from 9.0 to 13.8 N. While there is minimal impact of WC thickness on roughness and tribological behaviors, it does affect fracture toughness at greater indentation depths. Notably, at a WC thickness of 491 nm, the WC-C/DLC coated steel exhibits optimal fracture toughness, with a surface roughness of 112 nm, H of 18.7 ± 3.5 GPa, E of 182 ± 31 GPa, and a COF of 0.1. This study proposes methods to strengthen the adhesion between WC and DLC and examines how WC-C thickness affects the mechanical properties of WC-C/DLC, potentially enhancing wear resistance and reliability.