Evaluation of interface reactions in thermal barrier ceramic coatings

In this study, the interface reactions in thermal barrier ceramic coatings (TBCs) on AISI 304L stainless steel substrates were investigated. The plasma-spray technique was employed to deposit metallic and ceramic powders such as MgZrO₃, NiAl + MgZrO₃ and NiCrAl + MgZrO₃ on the substrate. The porosity of these coatings, measured by an optical method, was found to be between 6 and 9%. Oxidation tests were carried out to evaluate the interface reactions in TBCs at temperatures of 800, 900 and 1000°C. The microstructures of the powders, coatings and oxidized coatings were examined by means of an optical microscope and X-ray 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 oxidation rate changed with temperature was initially linear and then exponential.