EVALUATION OF INTERFACE REACTIONS IN THERMAL BARRIER CERAMIC COATINGS

In this study, the interface reactions in thermal barrier ceramic coat ings (TBCs) on AISI 304L stainless steel substrates were investigated. The plasma-spray technique was employed to deposit metallic and ceram ic powders such as MgZrO3, NiAl+MgZrO3 and NiCrAl+MgZrO3 on the substr ate. The porosity of these coatings, measured by an optical method, wa s found to be between 6 and 9%. Oxidation tests were carried out to ev aluate the interface reactions in TBCs at temperatures of 800, 900 and 1000 degrees C. The microstructures of the powders, coatings and oxid ized coatings were examined by means of an optical microscope and X-ra y diffractometry. The results show that the oxidation kinetics depend strongly on oxide layer thickness, temperature, duration of oxidation and composition of the bond coat. It was also observed that the oxidat ion rate changed with temperature was initially linear and then expone ntial. (C) 1997 Elsevier Science S.A.