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.

Diamond-like carbon (DLC) films are well known for their excellent tribological properties; however, poor adhesion limits the practical applications of DLC films. In order to clarify the effect of atmospheric controlled IH-FPP (AIH-FPP) treatment for pretreatment on durability and adhesion of carbon steel AISI1045 coated DLC films, wear tests were carried out with a focus on the coating damage and delamination behavior. A Cr particle which indicates high chemical affinity to carbon which constitutes the DLC films was selected as shot material for the AIH-FPP treatment, and AIH-FPP was performed with two types of treatment conditions; the one generates the Cr transferred layer and the other generates the Cr diffused layer on the substrate surface. After AIH-FPP treatment, DLC films were coated on them by using an unbalanced magnetron sputtering (UBMS) method to a thickness of 2 m. The specimens which have a Cr diffused layer at substrate surface and DLC films on it indicated low friction coefficient and maintained the excellent wear properties in the long-term region compared with practical DLC coated specimens. Consequently, it can be concluded that AIH-FPP with Cr particle is appropriate pretreatment before the coating process to achieve high durability and adhesion.

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In this study, in order to improve the adhesion strength of diamond-like carbon (DLC) films, medium carbon steel specimens were treated by using an atmospheric-controlled induction heating fine particle peening (AIH-FPP) with Cr particles that have high affinity for DLC films. The AIH-FPP treated specimens were characterized using optical microscope, scanning electron microscope and energy dispersive X-ray spectrometer. It was found that a diffused layer of Cr was formed on the specimen surface that was treated with AIH-FPP. The modified layer was then coated with DLC films, and in order to investigate the adhesion strength of DLC films on the surface modified substrates, reciprocating wear and indentation tests were performed. It was revealed that a Cr diffused layer formed by AIH-FPP treatment improved the adhesion strength of DLC films against sliding loads and large plastic deformations. In addition, the adhesion strength of DLC films was improved by increasing the thickness of a Cr diffused layer and superior friction characteristics were maintained for a long time. These results suggest that a Cr diffused layer induced by AIH-FPP treatment is an effective method for improving the adhesion strength of DLC films. ［doi:10.2320/jinstmet.J2017006］ (Received February 21, 2017; Accepted April 10, 2017; Published May 19, 2017) Keywords: surface modification, diamond-like carbon, fine particle peening, induction heating, adhesion strength 1.