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5210 |
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Wednesday, June 07, 2017, Hall 26 12:10 PM Process Diagnostics, Sensors & Controls |
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In-situ acoustic monitoring of thermal spray process using
high-frequency impulse measurements
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Weifeng Luo* / University of Dortmund, Germany Matthias Haack/ Department of Materials Test Engineering, TU Dortmund University, Germany Jens Nellesen/ Institute of Materials Engineering, TU Dortmund University, Germany Wolfgang Tillmann/ Institute of Materials Engineering, TU Dortmund University, Germany Frank Walther/ Department of Materials Test Engineering, TU Dortmund University, Germany |
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In order to guarantee their protective function, thermal sprayed coatings must be free from cracks, which expose the substrate surface to e.g. corrosive media. Cracks in thermal spray coatings are usually formed because of tensile residual stresses. Most commonly, crack occurrence is determined after the thermal spraying process by examination of metallographic cross-sections of the coating. Recent efforts focus on in situ monitoring of crack formation by acoustic emission analysis. However, the acoustic signals related to crack propagation can be drowned by the noise of the thermal spray process. In this work high-frequency impulse measurement technique was applied to separate different acoustic sources by visualizing the characteristic signal of crack formation via quasi-real-time Fourier analysis. The investigations were carried out on a twin wire arc spraying process utilizing FeCrBSi as coating material. The impact of the process parameters on the acoustic emission spectrum was studied. By acoustic emission analysis global, integral information about the formed cracks is gained. The coating morphology as well as coating defects were inspected using lightmicroscopy on metallographic cross-sections. Moreover, the resulting crack patterns were imaged in 3D using X-ray microtomography. |