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The elastic constants of zirconia air plasma sprayed (APS) thermal barrier coatings (TBC) have been studied. Flat, self-standing and waterproofed samples were immersed in water between two 15 MHz transducers and irradiated at varying incidence. A theoretical transfer function was calculated for an unlimited isotropic plate with plane waves and the experimental transfer function was best-fitted. The average P and S waves velocities are 2560 m/s and 1710 m/s respectively and have variations lower than 3 % over a wide refraction angle range (0-60 degrees). The corresponding average Young's modulus E is 33 GPa. Thus, these TBCs may be well modelled by an isotropic material. Such a low E, compared to compact zirconia (241 GPa), agrees with the high void content (15%) and with the presence of a microcrack network in APS TBCs. These results prove the feasibility of nondestructive evaluation (NDE) of porous TBCs using ultrasonic surface acoustic waves (SAW).

Additional information

Authors: CRUTZEN H P, JRC Ispra (IT);LAKESTANI F, JRC Ispra (IT);NICHOLLS J R, Cranfield University, Beford (GB)
Bibliographic Reference: Paper presented: 1996 IEEE International Ultrasonics Symposium, San Antonio, Texas (US), November 3-6, 1996
Availability: Available from (1) as Paper EN 40205 ORA
Record Number: 199611484 / Last updated on: 1997-01-16
Original language: en
Available languages: en
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