Thermal Barrier Coatings Defect Detection With Planar Capacitive Sensor

Thermal barrier coating on the aero-engine heat-side components of the protection and thermal efficiency is more and more important,but it is difficult for current detection method to conduct a comprehensive testing and evaluation on thermal barrier coating defects,which is a big security risk for making the use of the coating.A new detection program based on planar electromagnetic/capacitance is proposed by our task force.The defect detection method of the thermal barrier coating based on the planar capacitive sensor is mainly researched,and the change of the coating thickness is mainly detected,thus laying a foundation for further comprehensive testing.A planar capacitive sensor which used to detect the defect of thermal barrier coating is designed by analyzing the detection mechanism of planar capacitive sensor.The signal penetration depth,signal intensity and the relationship between the sensor sensitivity and the electrode structure of the planar capacitive sensor are analyzed.The COMSOL finite element simulation software is used to optimize the design,and the feasibility of the design is verified.The design of the micro-capacitance detection circuit and the processing of the detection signal are completed.Two kinds of tiny capacitance detection methods based on PCap02 capacitance digital detection chip and AC digital lock-in amplification are proposed respectively,which can detect the capacitance signal between electrodes and deal with the data with MATLAB,which can improve the detection precision and efficiency.A testing platform of coating thickness defect was built up,and different samples were tested by planar capacitive sensor.The experimental results verify the feasibility of the thermal barrier coating defect detection with planar capacitive sensor,the experimental platform designed to distinguish the minimum coating thickness change of 25μm.