Effect of Cr diffused layer formed by AIH-FPP treatment on adhesion of DLC films to a carbon steel substrate

In this study, a diffusion layer of Cr was formed on the surface of a carbon steel by atmospheric-controlled induction heating fine particle peening (AIH-FPP) treatment, followed by coating of a diamond-like carbon (DLC) film in an attempt to provide a less expensive and facile method for the production of DLC-coated steels with superior adhesion to conventional methods. Frictional wear tests and indentation tests with Vickers indenter were conducted on these DLC-coated steel specimens, and adhesion to the substrate was investigated experimentally. It was revealed that the formation of a Cr diffused layer on the surface of the substrate by AIH-FPP treatment significantly improved the adhesion of the DLC film to the substrate under a sliding load and a large plastic deformation. In addition, frictional wear tests revealed that the thickness of the Cr diffused layer formed by AIH-FPP treatment has a significant influence on the adhesion of the DLC film to the substrate. A thicker Cr diffused layer with a thickness of about 100 µm imparted better adhesion of the DLC film to the base material, and the superior friction and wear characteristics of the DLC film were sustained up to 49000 wear cycles while the specimens with a Cr diffused layer thickness of about 40 µm and without a Cr diffused layer maintained low friction coefficients up to 36000 and 8000 wear cycles, respectively. These results suggest that the proposed film forming method with a Cr diffused layer formed by AIH-FPP treatment is superior to the conventional method and is very efficient as a technique to improve the adhesion of DLC films to a carbon steel substrate.