The Role of Initial Particle - Substrate Interaction on the Evolving Stress Patterns in TS Coatings

Thermally sprayed coatings develop significant stresses during deposition. Process monitoring using curvature measurements via the Insitu Coating Property (ICP) sensor, has shown that the stresses in the system at the first instance of particle and substrate interaction (the first pass during deposition) is significantly different than that at the later stages (the subsequent passes). This conspicuous variation in the stress could be attributed to a host of factors ranging from substrate’s temperature, roughness and residual stresses, to the particles’ adhesion. The role of particle adhesion is one of the major thrust areas in this study. Material properties such as contact angle, wetting and adhesion of the particles on the substrate have been found to influence the stresses generated in the coating. In order to substantiate this hypothesis a systematic study has been conducted using two different powders YSZ and Mo sprayed on various substrate materials. The result suggested that the stress development during first pass depends on substrate material and the processing parameters.