In the case of thermal insulation layers, chipping is often observed at the end of the blade, where the curve radii are very small. This failure is likely to be caused by tensile stresses perpendicular to the interface and by compressive circumferential stresses in convexly curved layers. A finite element method was used to calculate the stresses that build up during a heat cycle. The system examined consisted of a cylindrical substrate, an adhesive layer, and the APS thermal insulation layer. The viscoelastic properties of the materials were taken into account, which lead to stress relaxation of the samples, which is often determined by experiment. Creep data and modulus of elasticity of the thermal insulation layers show a large range of variation. This paper shows the influence of these broad variations on the development of the state of stress in the thermal insulation layers during a single thermal cycle. Paper includes a German-language abstract.

Yttrium oxide-stabilized zirconium dioxide is mainly used in thermal barrier coatings. However, the desired higher gas inlet temperatures have initiated the search for novel materials. Low thermal conductivity and high melting points are important criteria for the selection of these materials. This paper investigates a zirconate material with a pyrochlore structure and a high melting point. In addition, it investigates the sintering behavior of the coatings at elevated temperatures. Dilatometer tests are carried out at 1200 deg C for at least 70 hours. For samples which had been annealed for 24 hours at 1250 deg C, the change in the porosity distribution is determined by means of mercury porosimetry. The paper presents the first results of thermal cycling tests on a plasma-sprayed coating. These first results are very promising. Paper includes a German-language abstract.