采用磁控溅射方法在镍基单晶高温合金基体上沉积NiCrAlY 粘结层，电子束物理气相沉积方法(EB-PVD)沉积陶瓷层(7 mass%Y2O3-ZrO2).用X-射 线 衍射(XRD)、扫描电镜(SEM)等研究了EB-PVD热障涂层热循环过程中的相变，同时观察了样品 的形貌变化.结果表明，EB-PVD方法沉积的陶瓷层，其柱状晶粒簇拥成团，表面比较致密， 然而晶粒簇间存在间隙，允许柱状晶横向伸缩，使基体能在相对大的范围内自由膨胀.经高 温氧化后，陶瓷层表面变得疏松，柱状晶粒簇间距增大，随着热循环的继续进行，相邻较大 的间隙互相连接而形成微裂纹，并逐渐横向及纵向扩展.循环氧化比恒温氧化更易于产生显 微裂纹.1050℃热循环过程中，ZrO2正方相的c/a轴比值逐渐增加，Y2O3含量逐渐减 少，非平衡正方相逐渐分解成平衡正方相和立方相.循环300次后，观察到少量从平衡正方 相转变而来的单斜相.
A NiCrAlY bond coat had been deposited on a Ni- base single crystal superalloy by magnetron sputtering,and then a top coat (7 ma ss%Y2O3-ZrO2) had been deposited by electron beam-physical vapor depositio n (EB-PVD).The phase transformation of ceramic top coat was investigated and the surface morphology change of the samples was observed.It was found that the ZrO 2-7 mass% Y2O3 ceramic top coat deposited by EB-PVD showed columnar grain s which formed dense clusters and the surface was relatively dense.However there were gaps or holes among grain clusters,which allowed the lateral expansion and contraction of the ceramic columnar grains and allowed free expansion of the su bstrate over a relatively large range.After exposure to elevated temperatures,th e gaps among columnar grain clusters became larger.The relatively large gaps int erconnected into one another and formed microcracks.With thermal cycling going o n,the microcracks extended across and through the top coat.Also the Y2O3 con tent in nonequilibrium tetragonal phase decreased gradually,and the nonequilibri um tetragonal phase decomposed to equilibrium tetragonal and cubic phases.After 300 thermal cycles at 1050℃,small amount of monoclinic phase was formed from th e decomposition of the tetragonal phases.
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