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Ōsaka, Japan

Ushiro Y.,University of Hyogo | Ushiro Y.,Umetoku Co. | Okai D.,University of Hyogo | Yamamoto A.,University of Hyogo
Advanced Materials Research | Year: 2014

The fracture behavior and adhesion strength of CrN/Cr and CrN films on SKD61 substrates were investigated by a three-point bending test. The SKD61 substrates were coated with a film with multilayer of CrN/Cr and a single film of CrN by a physical vapor deposition (PVD). The fracture behaviors of CrN/Cr and CrN films at three-point bending test were observed by scanning electron microscopy (SEM). Adhesions of the CrN/Cr/SKD61 and the CrN/SKD61 were also evaluated using a scratch tester. The scratch test resulted in no great difference in the adhesion strength between the CrN/Cr/SKD61 and the CrN/SKD61. On the other hand, the three-point bending test showed a high adhesion of the CrN/Cr with the intermediate layer of Cr film compared to the CrN on the SKD61. © (2014) Trans Tech Publications, Switzerland. Source


Ushiro Y.,University of Hyogo | Ushiro Y.,Umetoku Co. | Okai D.,University of Hyogo | Yamamoto A.,University of Hyogo | And 3 more authors.
Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals | Year: 2013

Adhesion strengths and microstructures of TiN coatings on white layer composed of e nitride (Fe2-3N) were examined. In the present study a hot work tool steel, SKD61, was used for a substrate. The substrates were coated with TiN by physical vapor deposition (PVD). Specimens were prepared with changing the conditions for polishing the surface of the substrate, and conditions for nitriding before PVD treatment. Peeling of the coated film occurred on un-polished specimen surface. Other specimens can be coated with TiN film without peeling. The microstructures, phase identifications and adhesion strengths were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), scratch tester and Rockwell adhesion tester, respectively. The black layer formed between the TiN film and white layer was observed by SEM, which generally deteriorates adhesion strength. However the scratch tests showed that the adhesion strengths of the specimens with black layer were higher than those on the specimen without the black layer. The black layer would not always decrease the adhesion strength. © 2013 The Japan Institute of Metals. Source


Ushiro Y.,University of Hyogo | Ushiro Y.,Umetoku Co. | Okai D.,University of Hyogo | Yamamoto A.,University of Hyogo | And 3 more authors.
Nippon Kinzoku Gakkaishi/Journal of the Japan Institute of Metals | Year: 2014

Three-point bending tests have been carried out in order to observe the fractures behavior of coated TiN films and to evaluate adhesion strengths at interfaces between the films and substrates. The substrates were hot work tool steel, 51(061, with and without nitriding treatment, which were coated with TiN films by physical vapor deposition (PVD). Two types of specimens were, therefore prepared, one of which consisted of TiN surface layer and the substrate of 51(061 (TiN/SKD61), while in another one nitride layer was formed between them (TiN/Nitride layer/SKD61). Scratch tests were also carried out for comparison. Specimens with 20L mm × 6w mm × 0.5t mm were cut from the coated specimens including the coated surface as L-W planes for using in bending tests. The specimen was set on the small bending device which had been developed by the authors, and then bent with referring to strain obtained from a strain gauge glued on the specimen. The specimen was set into SEM for observation. The L-W and L-t surfaces of the specimen were observed. Bending deformation and observation on the same areas were intermittently carried out until the substrate was fractured. On the specimen without the diffusion layer, cracks initiated at the surface of the TiN film and penetrated into the film in the perpendicular direction to the interface. The cracks arrested at the interface. Delamination of the TiN film from the substrate did not occur at the interface, but cracks initiated in the interior of the TiN film and propagated parallel to the interface, which caused fragmentation of the TiN film. Adhesion strength between the TiN film and the substrate was higher than the fracture stress of the TiN film. © 2014 The Japan Institute of Metale and Materials. Source


Ushiro Y.,University of Hyogo | Okai D.,University of Hyogo | Yamamoto A.,University of Hyogo | Fukushima Y.,Umetoku Co. | And 4 more authors.
8th Pacific Rim International Congress on Advanced Materials and Processing 2013, PRICM 8 | Year: 2013

TiN coatings on white layer composed of ε nitride (Fe2-3N) were studied to improve adhesion strengths. A hot work tool steel, SKD61, was used for a substrate. The substrates were coated with TiN by physical vapor deposition (PVD). Specimens were prepared with changing the conditions for polishing the surface of the substrate, and conditions for nitriding before PVD treatment. Adhesions of the TiN coating were evaluated using a Rockwell indentation tester and a scratch tester. The scratch tests showed that the adhesion strengths of the specimens with white layer were higher than those on the specimen without the white layer. The white layer which is formed in the nitriding process before PVD coating have little adverse effect on the adhesion of TiN film, although polishing the surface of the white layer improved the adhesion. Source

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