Correlation of In-Situ Curvature Measurement and Hole-Drilling Method for Evaluation of Stress States in Thermally Sprayed Coatings

The residual stresses within plasma sprayed coatings are an important factor which can influence the lifetime of the coatings crucially. It is very challenging to determine the stress profiles in these coatings since diffraction methods either show a low penetration depth (XRD) or are very complex and time consuming (neutron- and synchrotron-diffraction). The in-situ curvature measurement during deposition and post-deposition cooling is a powerful tool to determine the stress profiles in the as-sprayed coatings. However, there is no possibility to evaluate the change of the stress profile during the lifetime by this method. Therefore the hole-drilling method, which is used already for determination of near-surface stress profiles in single materials, is optimized to allow its application for coating systems. By correlating the curvature measurement and the hole-drilling method for the as-sprayed coatings one can calibrate the latter. This offers the possibility to determine the change of the stress profiles during the lifetime of the coatings.