Rietveld全谱拟合方法研究热障涂层的相转变

Study on Phase Evolution of Thermal Barrier Coating by Rietveld Refinement

利用大气等离子喷涂的方法制备8YSZ热障涂层,将涂层进行高温时效处理。采用X射线衍射技术和Rietveld全谱拟合相结合的方法,研究8YSZ涂层在高温时效条件下的相演化规律。结果表明,8YSZ原始态粉末主要为稳定四方相(t-ysz)结构,而喷涂态涂层则以亚稳态四方相(t'-ysz)为主。高温时效后,随温度的升高和时效时间的延长,t'-ysz逐渐分解形成t-ysz和c-ysz,各相含量在高温时效处理前10 h变化显著,10 h以后趋于平缓。随相变的进行,t'-ysz的微应变也不断变化。当温度高于1200℃时,相变加剧,t'-ysz的微应变也随之急剧上升。高温时效过程中,涂层未发生t-ysz→m-ysz马氏体相变,具有良好的相稳定性。

8wt% Yttria stabilized zirconia（8YSZ） thermal barrier coatings were fabricated by atmospheric plasma spraying. The coatings were exposed to high temperatures and phase evolution of 8YSZ coatings was investigated by a combination of X-ray powder diffraction and Rietveld refinement. The results show that,8YSZ powder mainly consistes of stable tetrgonal phase structure,while the as-sprayed coating mainly containes metastable tetragonal phase. The phase composition changes signific-antly in the first 10 h and then leveles off gradually with the extension of temperature and time.The microstrain in t＇-ysz phase is also constantly changing. Particularly,when the temperature is higher than 1200 ℃,the phase change exacerbates,which leads to a sharp increase in the microstrain level in t＇-ysz phase. The thermal barrier coatings don＇t occur the martensiti-c phase transformation from t-YSZ to m-YSZ during the aging treatment of thermal barrier coatings,which proves an excellent phase stability.