IR Thermographic Imaging - A Powerful Tool for On-Line Process Control of Thermal Spraying

Abstract

Abstract Many thermal spray coating applications require an optimum performance regarding the thermal and mechanical stability of the layer composite. The maximum loads that a composite can sustain, are not only dependent on the intrinsic material properties of the coating, but are also subject to the quality of deposition. The quality of the coating is predominantly influenced by the temperature distribution during the deposition process thereby influencing the residual stress development. Therefore failure of a thermally sprayed coating under mechanical and/or thermal load often could be avoided by an adequate deposition process with well controlled heat and mass transfer, i. e. by avoiding hot-spots on the surface that result in high residual stresses in the composite. With the help of Infrared (IR) thermography an imaging of the lateral and spatial temperature field of a workpiece surface and its evolution in time can be monitored and visualised. In the presented work the atmospheric plasma spraying process serves as an example to demonstrate the suitability of thermographic imaging as a quality control and process optimisation technique for online process monitoring and control in thermal spraying. The results indicate that IR-thermography can be used as a flexible tool for on-line process control of coating manufacturing via thermal spraying, it offers a powerful way to optimise the deposition process.