Research On The Structural State Of Thermal Barrier Coatings Of Turbine Blade By Ultrasonic Testing

With the development of high-performance aircraft engine, the continuousimprovement of thrust-weight ratio and the performance optimization.Attached to thesignificantly raised temperature of turbine gas, causing the working condition of turbineblade getting worse.In condition of high temperature, pressure and corrosion, it has been difficult toensure the safe and quality of the job, just rely on cooling technology and improve themanufacturing process of turbine blade. Therefore, thermal barrier coatings emerged asthe required. But the different of thermal expansion coefficient between thermal barriercoatings material and substrate alloy material, there might be cracks, porosity and otherdefects in the process of coating preparation. These flawed thermal barrier coatings willaffect the quality and life span of turbine blades seriously.In this paper, establish2d thermal barrier coatings model, simulation the ultrasonicpropagation characteristics in thermal barrier coatings, based on the finite elementsimulation software ABAQUS. Then combined with flooding focused ultrasound pulseexperimental analysis of the reflection echo at the interface and the ultrasound structuralstate of thermal barrier coatings.Firstly, establish thermal barrier coatings model to measurement the acousticvelocity of the ceramic layer, the adhesive layer and the substrate, then research theprocess of reflection of ultrasonic propagation in thin layers. As the size difference ofthe acoustic impedance between the three materials are not distinctness, causing theinterface reflection signal weakly.Secondly, reflection echo contains a large number of structural characteristics ofinformation, including sound velocity and frequency, so it must extract all the weaklyinterface reflection signal to detect the structural state of the coatings. And then extractthe state feature information by analysis the reflection signals. The introduction of thewave packet decomposition technology will used on decomposing the aliasing echosignal caused by thin layers, and identify the structural state of the feature informationin coatings which reflected by the echo signals.Finally, Plasma spray coating preparation method used into produce the thermalbarrier coating test block of turbine blades, and create a two-layers structure coating testblock. Coating materials composed of the ZrO2and Y2O3, the thickness of coating be in the range of0.1mm to0.15mm. Ultrasound flooding focused pulse reflection methodused to study the coating test block in experiment, complete the experiment testing,summarizes the experimental results.