EB-PVD热障涂层热循环过程中粘结层的氧化和相结构

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

采用磁控溅射方法在镍基单晶高温合金基体卜沉积 Ｎｉ３０Ｃｒ－１２Ａｌ－０．３１Ｙ（质量分数、％）粘结层，采用电子束物理气相沉积方法（ＥＢ－ＰＶＤ）沉积 ７％Ｙ２Ｏ３（质董分数）－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（冷却时会转变成单斜相）和立方相 ＺｒＯ２１０５０Ｃ循环 ２００次，粘结层氧化物（Ａｌ２Ｏ３）厚度约为３ｕｍ，表明ＮｉＣｒ－Ａｌ－Ｙ适宜作粘结层 继续热循环，陶瓷层中出现单斜相，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．

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 mum thickness consists of Al2O3 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)(2)O-4 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.