|
1288 |
|
Wednesday, June 04, 2008, Room 08 4:40 PM Ceramics Coatings for wear resistance and high temperature applications |
|
Thermal behavior of thermally sprayed CaZrO3 coatings |
|
Eugenio Garcia* / Instituto de Ceramica y Vidrio (CSIC), Spain Cristina Cano / Instituto de Ceramica y Vidrio (CSIC), Spain Thomas W. Coyle/ Centre for Advanced Coating Technologies (U. of Toronto), Canada Maria Isabel Osendi/ Instituto de Ceramica y Vidrio (CSIC), Spain Pilar Miranzo/ Instituto de Ceramica y Vidrio (CSIC), Spain |
|
The high temperatures developed during thermal spraying can modify the composition of the ceramic powder used as feedstock. Depending on the specific thermal spraying technique used, this modified composition may drive to distinct crystalline phases that may affect the final properties of the coatings. In this way, it is important to control the composition and phase evolution in order to improve the performance of these types of coatings in a specific application. The aim of this work was to analyse the effect of the deposition technique, air plasma and flame spray processes, on the microstructure and properties of calcium zirconate (CaZrO3) coatings. This ceramic material can be considered as a good candidate for thermal barrier applications due to its good corrosion resistance and low thermal conductivity. The microstructural characteristics and crystalline phases of the coatings were comparatively studied using X-ray diffraction and scanning electron microscopy (SEM-EDS). Possible changes in chemical composition were also analysed by x-ray fluorescence spectroscopy. Vickers tests and image analysis were used to determine hardness and porosity of the coatings. The thermal behaviour was analysed from laser-flash thermal diffusivity measurements done for freestanding specimens of 500 ¥ìm in thickness. Thermal treatments at temperatures ranging from 1000 and 1200 ¨¬C were carried out to evaluate the phase evolution in the coatings at high temperature, which can be explained considering the particle temperatures and observed CaO volatilization in each spraying technique as well as the information supplied by the ZrO2-CaO equilibrium phase diagram. |