等离子体喷涂纳米结构氧化锆热障涂层高温煅烧后的组织结构和相组成变化

Change of the microstructure and phase composition of plasma-sprayed nanostructured zirconia thermal barrier coatings after high temperature calcination

采用国产和进口两种大气等离子体喷涂设备，在不同功率下喷涂制备了ZrO2～8％（质量分数）Y2O3纳米结构热障涂层。在大气环境箱式电阻炉中1100～1250℃下对涂层进行了高温煅烧处理，采用扫描电子显微镜观察分析了涂层煅烧前后的微观组织变化，通过X射线衍射分析了涂层煅烧前后的相组成变化。结果表明：涂层经高温煅烧后，熔化团聚体大颗粒中新形成的纳米晶发生了明显长大，但临界熔化状态的团聚大颗粒中的小颗粒无明显变化；采用国产设备较低功率制备的纳米结构氧化锆涂层相组成为四方相和立方相，以四方相为主，经高温煅烧后四方相向立方相转变，且随煅烧温度和时间的增加而增加；采用进口设备较高功率制备的涂层全部为立方相，煅烧前后无相变发生。

ZrO2-8wt%Y2O3 nanostructured thermal barrier coatings were fabricated on nickel substrate by both domestic and foreign plasma spray equipments. Coating samples were heat-treated in a box furnace in air at a temperature from 1100-1250℃. Scanning electron microscopy was used to examine the change of microstructure and X-ray diffraction was used to analyze the change of constituent phases before and after the high temperature calcination. The results show that the nano-grains newly formed in the molten agglomerates grew obviously during the high temperature calcination, but the small particles of the large nearly molten agglomerates didn＇t grow. The coating fabricated by domestic equipment at lower power level consists of both tetragonal and cubic phases, and the main phase is tetragonal. During high temperature calcination the tetragonal phase transformed into cubic. With the calcination temperature and time increasing, more cubic phase formed. The coating fabricated by foreign plasma spray equipment at higher power level consists of only cubic phase, and no phase change was found after the high temperature calcination.