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3027 |
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Wednesday, September 28, 2011, Saal B2.1 9:25 AM Cold Spraying 3 |
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Deposition behavior and adhesion strength of cold-sprayed TiO2 particles |
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Motohiro Yamada* / Toyohashi University of Technology, Japan Michelle Dickinson / The University of Auckland, New Zealand Koichiro Shima/ Toyohashi University of Technology, Japan Noviana Tjitra Salim/ Toyohashi University of Technology, Japan Hiromi Nakano/ Toyohashi University of Technology, Japan Masahiro Fukumoto/ Toyohashi University of Technology, Japan |
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Cold-spraying has been developed as a high-quality metallic coating process. Recently, it became possible to fabricate a brittle ceramic coating using a particular nano-structured titanium dioxide (TiO2) powder. This coating is suitable for a wide range of photocatalytic applications. However, the adhesion strength of the coating should be improved. In order to improve the adhesion strength of the coatings, it is necessary to understand the bonding mechanisms. In this study, the bonding mechanisms between cold-sprayed TiO2 particle and stainless steel substrate was investigated by cross-section observation and quantitative adhesion strength measurement for the individual particles. The adhesion strength was measured by the combination using of scanning probe microscope (SPM) imaging and nano scratch test. The result clearly revealed a correlation in adhesion strength with splat size. The smaller splat size exhibited higher adhesion strength, though it is generally difficult to penetrate the cold-sprayed small particles through a shock wave formed in front of the substrate. The cross-section microstructure of the splat prepared by focused ion beam (FIB) showed the particular deposition behaviour of the TiO2 particle. The collided particle didnt deform the substrate surface and deformed the particle itself. The bottom centre of the splat is densified by the deformation and the other parts maintain the porous structure or broke up. Hence the higher adhesion strength of smaller splat was caused by this typical TiO2 deposition behaviour. |