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5085 |
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Analysis of ultrasonic-assisted laser re-melting of thermal barrier coatings |
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Zhengjie Fan / Department of Mechanical Engineering
Xian Jiaotong University, P.R. China Xia Dong / State Key Laboratory for Manufacturing Systems Engineering,Xi2an Jiaotong University, P.R. CHINA Rujia Wang/ State Key Laboratory for Manufacturing Systems Engineering,Xi2an Jiaotong University, P.R. CHINA Kedian Wang/ State Key Laboratory for Manufacturing Systems Engineering,Xi2an Jiaotong University, P.R. CHINA Wenqiang Duan/ State Key Laboratory for Manufacturing Systems Engineering,Xi2an Jiaotong University, P.R. CHINA Xuesong Mei/ State Key Laboratory for Manufacturing Systems Engineering,Xi2an Jiaotong University, P.R. CHINA Wenjun Wang/ State Key Laboratory for Manufacturing Systems Engineering,Xi2an Jiaotong University, P.R. CHINA Jianlei Cui/ State Key Laboratory for Manufacturing Systems Engineering,Xi2an Jiaotong University, P.R. CHINA |
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The effect of ultrasonic vibration, which was injected into the melt during the entire stages of re-melting, on the crack distribution, surface morphology, and grain refinement in a laser re-melted ZrO2-7wt% Y2O3 thermal barrier coatings (TBCs) was researched. Prefect uniform distribution of segmented network cracks and refined microstructure were obtained with the application of ultrasonic vibration. The increased fracture toughness, resulting from greater strain tolerance of the uniformly distributed cracks in ultrasonic-assisted laser re-melted TBCs, was confirmed by the thermal shock experimental verification and theoretical analysis. Visible ribbon-like loops, which appeared at surface ripples and were caused by surface tension, were eliminated during ultrasonic-assisted laser re-melting due to enhancement in surface convection. The surface morphology results indicated that the outline of re-melted coating surface obtained by utilizing the ultrasonic vibration with low power output (~20%) was much flatter compared to that obtained without laser re-melting. Moreover, evident undulated crests and troughs geometries appeared at the re-melted surface when ultrasonic vibration with high power output (above 50%) was introduced. The results of X-ray diffraction exhibited that the transformation from tetragonal to monoclinic was prevented when the power output of ultrasonic vibration was higher than 30%. Keywords: laser re-melting; thermal barrier coating; ultrasonic vibration; surface morphology; network crack distribution; grain refinement. |