The influence of plasma spraying parameters on the mechanical properties of coatings has been studied. ZrO2-Y2O3 coatings were sprayed onto stainless steel and aluminium substrates at temperatures of about 75°C and 225°C. An original set of samples, facilitating the measurement of substrate deflection, was used to evaluate the effect of thermal cycling under different spraying conditions. In order to correlate thermal cycling values and mechanical properties to coating microstructure, the coatings were impregnated with low-viscosity resin and examined under a confocal microscope. The results reveal the influence of spraying temperature, substrate properties, and torch-substrate velocity on coating damage.

Thermal spraying induces stresses, which strongly influence thermomechanical properties of the deposits. To study both generation and influence of these stresses, various techniques could be used separately and/or concurrently. "In-situ" curvature, neutron diffraction and incremental hole drilling methods are often presented as complementary techniques. In this study, partially stabilized zirconia coatings, performed onto steel substrates at various spraying temperatures, have allowed to compare these three different methods.

The thermomechanical properties of plasma-sprayed deposits strongly depend on residual stress distribution. This latter is mainly attributed to the relative torch/substrate velocity as well as to the cooling system location and efficiency. The determining of both quenching and thermal stresses, which are generated respectively during spraying stage and cooling stage, is then required to improve coatings quality. A rather simple apparatus, which consists in monitoring the curvature of a beam substrate during the whole deposition process, has been developed to work under industrial conditions. It has been applied to partially stabilized zirconia coatings performed onto stainless steel and cast iron substrates. Spraying temperature and plasma gun velocity have been selected as relevant parameters for this study about stress generation and mechanical release. Finally, four point bend tests have been performed on deposited samples to measure coating mechanical properties and to evaluate damage level.

In order to determine residual stresses in industrial plasmasprayed coatings, a rather simple apparatus, which monitors the curvature of a beam substrate during the deposition process, has been developed. The experimental set-up consists of a water-cooled rotating cylinder, holding an initially plane substrate, whose curvature is continuously measured using a contacting displacement sensor disposed into the cylinder. The combination of the plasma gun translation and the cylinder rotation allows to reach industrial spraying velocities. Liquid argon cryogenic system is used to control the substrate temperature from about 50°C to more than 300°C independently from the process velocity. A typical recording is analyzed thoroughly and a theoretical approach to residual stress calculation discussed. This method is applied to partially stabilized zirconia coatings performed onto stainless steel substrates for spraying temperatures between 80°C and 210°C.