Correlations Between Microstructure and Mechanical Properties of Air Plasma‐Sprayed Thermal Barrier Coatings Exposed to a High Temperature |
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| Authors: | Julián D Osorio Deiby Maya Augusto C Barrios Adrián Lopera Freddy Jiménez Juan M Meza Juan P Hernández‐Ortiz Alejandro Toro |
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| Affiliation: | 1. Materials and Minerals Department, National University of Colombia, , Medellín, Colombia;2. Department of Mechanical Engineering, Florida State University, , Tallahassee, Florida, 32306;3. Mechanical Engineering, National University of Colombia, , Medellín, Colombia;4. Mechanical Engineering, University of Alberta, , Edmonton, AB T6G 2G8 Canada;5. Tribology and Surfaces Group, National University of Colombia, , Medellín, Colombia;6. BioTechnology Center, Genomics Center of Wisconsin, University of Wisconsin‐Madison, , Wisconsin, 53706 |
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| Abstract: | An indentation method is used to study the variations in Young's modulus, hardness and fracture toughness of air plasma‐sprayed thermal barrier coatings at a high temperature. The coatings were exposed to 1100°C during 1700 h. A sudden increase in Young's modulus for the first 600 h was observed, while the hardness increased after 800 h as a consequence of sintering. Conversely, there was a reduction of 25% in fracture toughness after 1700 h, evidencing the thermal barrier coating degradation. The evolution of these mechanical properties was correlated with microstructural changes. After 1700 h, the thermally grown oxide thickness reached 6.8 μm, the volumetric percentage of porosity was reduced from 6.8% to 4.7% and the amount of monoclinic phase increased to 23.4 wt%. These characteristics are closely related to the stress distribution in the top coat, which promotes cracks nucleation and propagation, compromising the coating durability. |
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