EB-PVD热障涂层热循环过程中粘结层的氧化和相结构

采用磁控溅射方法在镍基单晶高温合金基体上沉积Ni-30Cr-12Al-0.3Y（质量分数，％）粘结层，采用电子束物理气相沉积方法（EB－VPD）沉积7％Y2O3（质量分数）－ZrO2陶瓷顶层，结果表明，在热循环过程中，非平衡相t′-ZrO2中的Y2O3含量逐渐减少，t′－ZrO2相逐渐分解成平衡相t-ZrO2（冷却时变转变成斜相）和立方组ZrO2,1050℃循环200次，粘结层氧化物（Al2O3)厚度约为3μm，表明Ni-Cr-Al-Y达宜作粘结层，继续热循环，陶瓷层中出现单斜阳，粘结层中Al贫化，氧化层中出现NiO及尖晶石等，引起应力集中，导致涂层失效。

OXIDATION AND PHASE STRUCTURE OF THE BOND COAT IN EB-PVD THERMAL BARRIER COATINGS DURING THERMAL CYCLING

After depositing Ni-30Cr-12Al-0.3Y(mass fraction, %) bond coat on a Ni base single crystal superalloy by magnetron sputtering, a ceramic top coat(7%Y2O3-ZrO2) was deposited by electron beam-physical vapor deposition(EB-PVD). During thermal cycles, the Y2O3 content in non- equilibrium phases t'-ZrO2 decreased gradually and the t'-ZrO2 decomposed gradually to equilibrium t-ZrO2(transforming to monoclinic phase after cooling) and cubic ZrO2 phase. After 200 thermal cycles, the thermally grown oxides(TGO) layer with 3 um thickness consists of Al2O2 exclusively, indicating that the sputtered Ni-Cr-Al-Y coating is suitable as bond coat for EB-PVD thermal barrier coatings. With increasing thermal cycles, a small amount of monoclinic m-ZrO2 formed from t-ZrO2. Al was depleted, and NiO and Ni(Al, Cr)2O4 formed near the interface between TGO and bond coat. Stress concentration due to oxide growth and phase transformation between t-m ZrO2 would weaken the combination between top and bond coats, and then cause thermal barrier coating to spall from the substrate.