| About this Abstract |
| Meeting |
MS&T22: Materials Science & Technology
|
| Symposium
|
Phase Transformations in Ceramics: Science and Applications
|
| Presentation Title |
Crystallization Kinetics of Yttria-doped Ytterbium Disilicate Environmental Barrier Coatings |
| Author(s) |
Dawson Smith, Molly O'Connor, Robert Golden, Marshall Sweet, Rodney Trice, Michael Titus |
| On-Site Speaker (Planned) |
Dawson Smith |
| Abstract Scope |
Yttria-Doped Ytterbium Disilicate (Y/YbDS) environmental barrier coatings protect Ceramic Matrix Composites (CMCs) in gas turbine engines from reaction with the atmosphere. These coatings are partially amorphous due to high cooling rates in atmospheric plasma spray deposition - thus, they must be crystallized with a heat treatment before use. Crystallization and thermal expansion can crack the coating if the heat treatment is not properly designed. No current study has facilitated design of crack-free heat treatments using crystallization kinetics and strains of Y/YbDS. To do this, we used Differential Scanning Calorimetry (DSC), employing the Ozawa-Flynn-Wall kinetic analysis and Avrami-Erofeev reaction model to calculate transient activation energy, pre-exponential factor, and mechanism of crystallization. These models indicated that activation energy and pre-exponential factor increased during crystallization, while the local Avrami exponent indicated that crystal growth is three dimensional and diffusion-controlled, and that nucleation rate increases with heating rate. Crystallization strains were confirmed with dilatometry. |