Title :
Ultrasonic characterisation of thermal barrier coatings
Author :
Crutzen, H.P. ; Lakestani, F. ; Nicholls, J.R.
Author_Institution :
JRC-IAM, Eur. Commission, Ispra, Italy
Abstract :
The elastic constants of zirconia air plasma sprayed (APS) thermal barrier coatings (TBCs) 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 deg.). 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 NDE of porous TBCs using ultrasonic SAW
Keywords :
Young´s modulus; ceramics; coatings; elastic constants; plasma arc sprayed coatings; porous materials; surface acoustic waves; thermal insulating materials; transfer functions; ultrasonic materials testing; zirconium compounds; 15 MHz; NDE; P waves; S waves; Young´s modulus; ZrO2; elastic constants; isotropic plate; microcrack network; plane waves; porous TBC; transfer function; ultrasonic SAW; void content; zirconia air plasma sprayed thermal barrier coating; Bonding; Ceramics; Coatings; Lakes; Size measurement; Thermal spraying; Thickness measurement; Transducers; Transfer functions; Ultrasonic variables measurement;
Conference_Titel :
Ultrasonics Symposium, 1996. Proceedings., 1996 IEEE
Conference_Location :
San Antonio, TX
Print_ISBN :
0-7803-3615-1
DOI :
10.1109/ULTSYM.1996.584078
