Stable crack propagation in free standing thermal sprayed Al2O3 and Al2O3ZrO2TiO2 coatings

Due to their unique properties and structure, thermally sprayed ceramics are applied in many fields. Their applications range from engineering ceramics to the use in high temperature units, especially since an improved thermal shock performance was observed. The present study presents an analysis of structural and mechanical properties of thermal sprayed alumina-rich coatings at room temperature. Microstructure and phase composition were analysed by scanning electron microscopy and X-ray diffraction. For pure alumina material, high temperature X-ray diffraction was performed additionally and yielded a phase transition within heating to 1200 °C. Micrographs present typically layered and chaotic microstructure, streaked by microcracks. Cyclic loading test-procedures and the resulting load-displacement-curves revealed a pronounced R-curve-behaviour for coatings of pure Al2O3 and Al2O3 ZrO2 TiO2 compositions.