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Crack Growth Tests in Air Plasma-Sprayed Yttria Coatings for Alumina Ceramic Matrix Composites

German Aerospace Center (DLR), Institute of Materials Research, D-51170 Cologne, Germany
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Ceramics 2019, 2(3), 514-524; https://doi.org/10.3390/ceramics2030039
Received: 26 June 2019 / Revised: 16 July 2019 / Accepted: 1 August 2019 / Published: 19 August 2019
Yttria coatings for all-oxide combustor walls were tested for their crack-growth behavior. These environmental and thermal barrier Y2O3-coatings were processed by atmospheric plasma spraying (APS). The stiffness and strength were measured for as-received and aged samples that were heat treated at 1000 °C, 1100 °C and 1200 °C for a 10 h dwell time. The results show a clear development with respect to the aging conditions. The changes of the modulus and the bending strength indicate that the microstructural changes are not completed, even after aging at 1200 °C for 10 h. The fracture toughness was tested for different orientations on samples aged at 1200 °C. Bending tests as well as indentation experiments were conducted. Furthermore, a bending device was designed to observe the crack-growth in situ. The device had to be rigid and is driven by a piezo stack. The crack growth resistance shows differences in the rise of the R-curves for different orientations of the crack propagation. This is in agreement with the microstructure that results from the plasma spray process. View Full-Text
Keywords: yttria; plasma spraying; EBC; CMC; mechanical testing; crack growth resistance yttria; plasma spraying; EBC; CMC; mechanical testing; crack growth resistance
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Hackemann, S.; Bartsch, M. Crack Growth Tests in Air Plasma-Sprayed Yttria Coatings for Alumina Ceramic Matrix Composites. Ceramics 2019, 2, 514-524.

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