Determination of thermal sprayed coatings elastic modulus using four point bending test

The four point bending scheme was adopted to evaluate the in plane elastic modulus of a NiCoCrAlY-ZrO2(Y2O3) thermal barrier coating, employed for gas turbine applications. Four experimental techniques have been set up, based on mesurement of mid section strain and displacement. Two specimen geometries and several substrate thicknesses were employed. Being the ratio of the coating to the substrate thickness generally small, a preliminary sensitivity analysis, based on errors propagation theory, was focused on the identification of the main sources of measurement uncertainties, in relation to the various techniques. Measures were performed from room temperature up to 500 degrees C. Experimental results are reported and the importance of a correct estimate of the layers thickness discussed.