Effect of fine particle bombardment treatment on tribological properties and adhesion of DLC film coated on SCM440 steel

To improve poor adhesion of Diamond-like Carbon (DLC) coatings on the steel substrate, Fine Particle Bombardment (FPB) using Cr based shot particles are combined with DLC coating process. The FPB treatment distributes diffused Cr elements onto the treated surface, creating a Cr-rich layer. The FPB treatment increases the surface hardness and roughness. Wear test was conducted to compare the tribological properties of the DLC coated FPB treated steels and that of the DLC coated non FPB treated ones with a special focused on the Cr-rich layer, surface hardness and roughness. The DLC coated surface, after FPB treatment, kept low friction coefficient, while the DLC coated non FPB treated ones showed a sudden increase indicating the delamination of DLC layer. This is because of Cr-rich layer, which increase adhesion between DLC coating and steel substrate.