Thermal expansion coefficient of a NiCoCrAlY-ZrO_{2(Y_{2O_{3) coating by a digital image processing based dilatometer

A procedure for thermal expansion coefficient measurement is presented. A quartz dilatometer and a digital image processing technique were employed to obtain an accurate measure of the elongation of a prismatic specimen placed in a tubular furnace. By testing several symmetrically coated specimens the thermal expansion coefficient of a NiCoCrAlY-ZrO2(Y2O3) coating was obtained. The relationships for deducing the coefficient of the coating were derived by the multi-layer beam model and their sensitivity to experimental errors was discussed. Results were obtained in the range 20°C-950°C, both for the substrate and coating materials. An estimate of results accuracy is given, based on a Monte Carlo simulation of uncertainties.