Alexander Soldatov

In recent years, CVD diamond-coated tungsten carbide (WC-Co) tools have been widely utilized due to their benefits in the machining of non-ferrous alloys and polymer composite materials, especially carbon-fiber-reinforced plastics (CFRPs). The reconditioning of such coated tools is economically attractive due to their high cost and short tool life. The decoating of the remaining diamond film from the used tools and the subsequent surface preparation by wet chemical pretreatment are essential steps for new CVD diamond film formation. Previously, it was shown that reactive ion beam etching (RIBE) could effectively remove CVD diamond films. However, some degree of WC-Co tool substrate damage is expected due to the high ion energy in RIBE and the chemical activity in wet etching. This study addresses the effects of RIBE decoating and surface pretreatment steps on WC-Co tools with a complex shape in terms of the ion-induced surface damage, geometry alteration, and adhesion of a subsequently re-applied CVD diamond film. Moreover, the cutting performance of the tools subjected to the RIBE decoating and repeated film deposition was studied via CFRP cutting tests. It has been shown that the RIBE decoated and recoated tools had a high level of cutting performance comparable to the new tools.

This study investigated the effect of boron-doped and undoped diamond coatings on the cutting performance of cobalt cemented tungsten carbide (WC-Co) drills when drilling CFRP. Three types of diamond coating, as boron-doped microcrystalline (B-MCD), boron-doped nanocrystalline (B-NCD), and undoped nanocrystalline (NCD), were deposited on specially designed for drilling of CFRP one-shot drills by the hot filament chemical vapor deposition (HFCVD) method. The coating characteristics, such as surface morphology, roughness, carbon structure, and interfacial adhesion, were investigated. Then cutting tests were carried out, and the tool’s flank wear, thrust force, and torque were evaluated. For comparison of cutting performance, non-coated WC-Co drills were used in the tests as well. Furthermore, drilled holes were inspected in terms of peel-up and push-out delamination. According to the results, the B-MCD coated drill presented advantages in tool life, and quality of drilled holes over the NCD and B-NCD coated drills. Also, the results confirmed the adhesion enhanced effect of diamond coating to WC-Co substrate through boron doping of the layer.