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3665 |
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Thursday, May 22, 2014, Hall H2 12:00 PM Power Generation - Industrial Gas Turbines 2 |
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The preparation of columnar-structured YSZ coatings deposited by plasma spray-physical vapor deposition using a shrouded plasma torch |
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Chang-Jiu Li / Xi'an Jiaotong University, P.R. China Qing-Yu Chen* / State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, China Cheng-Xin Li/ State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, China Guan-Jun Yang/ State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, China Jian-Zhuang Zhao/ State Key Laboratory for Mechanical Behavior of Materials, Xi'an Jiaotong University, China |
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Plasma spray-physical vapor deposition (PS-PVD), as an emerging process which is operated in a pressure as low as 100 Pa, is able to deposit ceramic coatings fast with columnar structure. The key issue is to heat ceramic powders to a complete evaporation state. With yttria stabilized zirconia (YSZ) powder, 180 kW class plasma spraying system is usually used for the deposition of the coating with a columnar structure. In this study, an 80 kW class plasma spraying system was used to fabricate columnar YSZ coatings by PS-PVD at a pressure of 100 Pa. A metal shroud was attached in the front of the plasma nozzle to restrain expansion of plasma jet and enhance the heating ability of plasma jet to spray powders. The torch was operated at an arc power of 45 kW and YSZ coatings was deposited at a powder feed rate of 0.2 g/min. Optical emission spectroscopy (OES) was used to diagnose the particle state in plasma jet. The surface morphology and fracture morphology of YSZ coatings were characterized by scanning electron microscope. It was found that the coatings with a columnar-structure can be successfully deposited at the present conditions. The results show that the fracture morphology changes from a columnar structure to a cauliflower structure with spray distance. An island or an angular morphology was recognized from the top surface of YSZ coatings. The results suggest that the YSZ coatings were deposited by the clusters or atoms which were obtained through complete evaporation of YSZ powder during PS-PVD processing. The relationship between the OES spectra and coating microstructure is discussed. |