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5435 |
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Influence of critical plasma spray parameters on properties to Cr2O3 coatings with online monitoring |
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Xin Wang* / University of Electronic Science and Technology of China, P.R. China Xiaoqiang Feng / University of Electronic Science and Technology of China, China Longjiang Deng/ University of Electronic Science and Technology of China, China Zhigang Li/ Advance Metallizing Supplies Ltd, China |
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Plasma spraying technology is one of novel surface modification process which has been developed rapidly in recent years. The Cr2O3 coatings deposited by plasma spraying are applied in various areas due to its excellent thermal barrier resistance. In this research program, the Cr2O3 bond coatings were deposited on the Q234 steel by plasma spraying with Praxair SG-100. Different spraying parameters were selected to obtain powders with different temperature and velocity. Average particle temperature, velocity were measured in situ by Accuraspray G3C online system. The microstructure and micro-hardness of coatings were measured by SEM and microhardness tester. The results showed that particle temperature decrease from 2612 °C to 2150 °C with spraying distance increase from 80 mm to 120 mm. Particle temperatures and velocity increase with spraying current and flow rate of hydrogen. Particle temperature slightly increase and particle velocity slightly decrease with increasing carrier gas flow rate. Particle temperature slightly decrease and particle velocity slightly increase with increasing argon flow rate. The temperature when particle reach the steel is mostly below melting point of Cr2O3. It is observed micro-hardness is independent of particle temperature and velocity. Porosity decreases with increasing particle temperature and velocity when particle temperature is below melting point. There are embedded spherical particles observed by SEM in coating when spraying particle temperature is higher than melting point. Liquid particles directly fly to substrate with high velocity, and then sputter into lots of small liquid particles, which solidify in spherical shape in very high cooling rate. Those embedded spherical particles may deteriorate mechanical property of coating with high porosity. |