Possibilities for Online Coating ThicknessMeasurement for Thermal Spray Processes
Coating thickness is a key economic factor for thermal spray coating solutions. In this work, an optical micrometer and a laser displacement sensor were investigated for use for online coating thickness measurement during thermal spraying. The suitability of these two measurement methods was investigated for APS and HVOF spraying of aluminum oxide. Measurements obtained online were compared with values obtained from commonly used offline methods. Both the optical micrometer and the laser displacement sensor were found to be suitable for online coating thickness measurement. Overpowering of the light source in APS and thermal expansion of the substrate in HVOF represented the main disturbing factors. The advantages of the optical micrometer are the lower scatter and higher stability of measurements. In contrast, the laser displacement sensor features greater flexibility in operation and can hence be used more easily for complex geometries.
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