Spatially varying microhardness in a platinum-modified nickel aluminide bond coat in a thermal barrier coating system

The hardness of a Pt-modified Ni aluminide bond coat and its ZrO2 top coat in an electron beam-physical vapor deposition ZrO2-based thermal barrier coating system has been studied as a function of temperature in as-deposited and aged (1200 °C/1 h) coupon samples, and in a used blade taken out of service after a (modest) fraction of life. A marked brittle to ductile transition at 580 ± 30 °C was observed in the as-deposited material, in agreement with previous uniaxial tensile data in this system. Significant spatial variation in the hardness of the bond coats were observed at room temperature and could be correlated with spatially varying microstructures.