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1530 |
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Microstructure observation on the interface between warm spray deposited titanium powder and steel substrate |
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KeeHyun Kim* / University of Birmingham, UK Makoto Watanabe/ National Institute for Materials Science, Japan Jin Kawakita/ National Institute for Materials Science, Japan Kazutaka Mitsuishi/ National Institute for Materials Science, Japan Tommy Wu/ University of Toronto, Canada Seiji Kuroda/ National Institute for Materials Science, Japan |
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Powder particles are heated to temperature below a melting point and deposited onto a substrate at high velocity in warm spraying. In order to achieve this, nitrogen gas is mixed with a flame jet generated by a commercial HVOF apparatus. High quality titanium coatings with negligible oxidation have been sprayed onto the steel substrate to increase the corrosion resistance. Microstructures formed in the interface region of titanium and steel are expected to affect strongly the mechanical properties of the resultant coatings such as adhesive strength. In the present report, Ti powders (TILOP -45?Ým) were deposited onto the carbon steel substrates, which were blast cleaned with alumina grit. Microstructures of the deposited titanium were observed by SEM and TEM. TEM sample was made in the cross sectioned region of the interface by focused ion beam lift-out technology. Ti powders were very highly deformed in the region of heavy deformation by impaction on the substrate whereas the steel substrate was apparently only slightly deformed. Since the deformed region should cool down very rapidly, possibly at the rate of 108~109 K/sec, it is expected to result in non-equilibrium structures such as an amorphous phase in the interface region. In TEM observation, a transition layer consisting of nano-crystals, oxides and amorphous phase was found at the interface. No interdiffusion or formation of compounds between Ti and Fe were observed |