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4154 |
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Friday, May 23, 2014, Hall H3 11:40 AM Pre- & Post-Treatment |
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Effects of spray parameters and heat treatment on the microstructure and mechanical properties of titanium coatings formed by warm spraying |
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Seiji Kuroda* / National Institute for Materials Science, Japan R. Molak / National Institute for Materials Science, Japan H. Araki/ National Institute for Materials Science, Japan M. Watanabe/ National Institute for Materials Science, Japan H. Katanoda/ Kagoshima University, Japan N. Ohno/ Plasma Giken Co., Ltd., Japan H. Fukanuma/ Plasma Giken Co., Ltd., Japan |
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Microstructure and mechanical properties of titanium deposits fabricated by warm spray were investigated in the as-sprayed and heat-treated conditions with an aim to find the optimal parameters of the spray and post-spray processing. The coatings were deposited with different nitrogen flow rates in a range from 0.5 to 1.5 m3/min. It was found that the temperature and velocity of in-flight particles, which were controlled by the spray parameters, have significant effect on the properties of the fabricated coatings such as porosity and oxygen content. Recently, the combustion pressure of warm spray (WS) has been raised from 1 to 4 MPa, resulting in increase in the particle velocity close to 1,000 m/s. This modificationhad significant beneficial effects in terms of improving density and controlling the oxygen level in titanium coatings.Mini specimens with total length about 9 mm were used to perform tensile tests. The optimal set of mechanical properties (Youngs modulus, ultimate tensile strength, yield strength and elongation to failure) was found for specimens formed with a middle range of nitrogen flow rate. Additionally,several post processing heat treatments were performed in order to enhance the mechanical properties of these as-sprayed coatings. It was found that post-processing heat-treatment allow to improve bonding between deposited particles,which resulted in significant enhancement of the strength and plasticity of the titanium coatings. |