The influence of physical properties and spraying parameters on the creation of residual thermal stresses during the spraying process

Abstract

Residual stresses in plasma-sprayed coating-substrate composite systems have positive or negative effects on the service life of components depending on the service loads involved. Thus the performance of these composite systems can be increased by influencing the residual stress curves. For this it is necessary to predict the residual stress curves as a function of the processing parameters and physical properties of coating material and substrate. In this paper a model is presented for calculation of thermally induced residual stresses, which is based on a temperature curve calculation model for temperature-dependent material data. The process type, e.g. atmospheric pressure or vacuum plasma spraying, is not of interest, because the model only takes into account the parameters that are relevant to the impinging of the particles, i.e. temperature, velocity, mass flow etc. Results for alumina and zirconia on austenitic and ferritic steel substrates are presented. The residual stress curves for alumina and zirconia on austenite are qualitatively similar. The coating thickness is shown to increase the stresses in the thicker coatings. The effect of reduced spraying distances on the residual stress values is minimal.