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4886 |
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Tuesday, May 10, 2016, Room 3E 12:10 PM Process Diagnostics, Sensors & Controls |
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Effect of spray kinetic parameters on coating properties in a shrouded plasma spraying process |
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Ting Liu / Tsinghua University, China Yaping Ma / Tsinghua University, China Lili Zheng/ Tsinghua University, China Guanzhong Zhang/ Tsinghua University, China Hui Zhang*/ Tsinghua University, China |
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Air plasma spraying process has been used for manufacturing a broad variety of functional coatings with high production and flexibility in operation. This technique has the drawback of unnecessary oxidation of spraying particles. Better use of this technique requires the control of the oxidation environment. Futher, quality of coatings such as microstructure with designed functionality, thickness homogeneity in coatings is strongly affected by sprays kinetic parameter such as path and angle, moving speed for the given spraying surface. Better quality in coatings requires the optimal control of spray kinetic parameters. This study aims to investigate spraying process by a designed shrouded plasma spray system. Specifically, the interaction between spray kinetic parameters and coating properties (microstructure and thickness) were studied. A coating build-up code was applied to predict porosity, thickness and roughness of coatings under different spray angles, moving speeds and scanning steps together with experimental investigation. The splat map was built and spatial distribution of splats was obtained through statistical analysis, while splat morphology was analyzed by optical microscope. The microstructure of coatings was observed by SEM and EPMA, and their porosities were measured through the image process. Results indicated strong influence of spray angle on the microstructure and thickness of coatings.. Reducing spray angle resulted in a thinner coating and higher porosity in coatings. Changing the torch translational speed affects mass and heat exchange between plasma flame and substrate. A constant torch movement is preferable for homogeneous coating thickness and properties. An optimized scanning step can be obtained with the given spraying material, process and spray kinetic parameters. |