Residual stresses in aluminium phosphate sealed plasma sprayed oxide coatings and their effect on abrasive wear

Effect of residual stresses on plasma sprayed alumina and chromia coatings sealed with aluminium phosphate were studied as a function of the temperature of the sealing treatment. Stresses were measured by X-ray stress analysis and high-speed circular microhole drilling method. Residual stress states were correlated with other coating properties such as microhardness, porosity, microstructure and dry abrasion wear resistance. Correlations were found between sealing treatment temperature, residual stress state and wear resistance. Wear resistance of the oxide coatings was increased at all sealing temperatures. Sealing treatment affected coatings by two mechanisms. Aluminium phosphate sealing induced compressive stresses to coatings and simultaneously bonded coating lamellar structure.