Papers by Author: K. Sakaguchi

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Authors: Yo-ichi Takeda, M. Bojinov, Hannu Hänninen, P. Kinnunen, T. Laitinen, K. Mäkelä, T. Saario, K. Sakaguchi, Tetsuo Shoji, P. Sirkiä, A. Toivonen
Abstract: A possible approach to describe the role of the environment in the phenomena behind crack initiation and crack propagation in stress corrosion cracking (SCC) is to assume that the transport of species through the oxide film on the material surface is one of the rate-controlling factors. The transport rates of ionic and electronic defects through the oxide film are, in addition to the environment, also affected by the stress and strain applied to the bulk material. In this paper, the surface oxide film formed on AISI 316L steel in slow strain rate tests (SSRT) in simulated BWR condition has been analyzed by using Electron Spectroscopy for Chemical Analysis (ESCA). The obtained film composition and structure have been combined with in-situ contact electric resistance (CER) measurements in order to evaluate the changes in oxide film electric properties during straining in the above environment. The results show that oxide film resistance of the strained part exhibits a maximum at around 2% of strain, which seems to correlate with a maximum in the Cr(III) concentration in the inner layer of the oxide. The implications of these results to SCC are discussed based on Mixed-Conduction Model (MCM).
Authors: Michel Jeandin, Dimitris Christoulis, Francois Borit, Marie Helene Berger, S. Guetta, G. Rolland, Vincent Guipont, Eric Irissou, Jean Gabriel Legoux, Christian Moreau, M. Nivard, L. Berthe, M. Boustie, W. Ludwig, K. Sakaguchi, Y. Ichikawa, Kazuhiro Ogawa, S. Costil
Abstract: Basically, thermal spray and laser processing can be considered as half brothers since they show many common features due to the use of a (more or less) high-energy source for both. Their combination can therefore be very fruitful and prominent to achieve coatings, which results in their most recent and advanced applications. In the materials processing development story, the laser will thus have moved from cutting to coating. This keynote presentation focuses on the recently-developed coupling of laser processing to cold spray). In this dual process, a cold spray gun is combined to a laser head in a single device, e.g. on a robot. Series of coating experiments using various laser irradiation conditions, primarily pulse frequency, were carried out for Al-based and Ni-based alloys. Laser pre-treatment of the substrate just prior to cold spray, was shown to be beneficial for adhesion of cold-sprayed coatings. Adhesion improvement was exhibited and studied from LASATesting (LASAT for “LAser Shock Adhesion Test”). Incidentally, through LASAT also, the role of lasers in the development of thermally-sprayed coatings can be considered as major. Results are discussed in the light of a TEM (Transmission Electron Microscope) study of the coating-substrate interface with and without laser pre-treatment.
Authors: S. Rangarajan, Douglas Shukert, Yo-ichi Takeda, K. Sakaguchi, Tetsuo Shoji
Authors: Y. Lu, K. Sakaguchi, Tetsuo Shoji
Abstract:          
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