热障涂层双层黏结层的高温氧化行为

采用箱式电阻炉研究了具有梯度热膨胀系数的（孔隙层+氧化层）双层黏结层结构热障涂层的高温氧化行为。采用气罩等离子喷涂在Inconel 738合金基材上制备60μm厚的孔隙层,通过超音速火焰喷涂（HVOF）在孔隙层上制备120μm厚的氧化层。在1000℃下对黏结层进行不同时间的高温氧化试验。结果表明,黏结层由孔隙层和氧化层组成;喷涂态孔隙层具有典型的层状结构,未出现明显氧化;喷涂态氧化层较为致密,内部弥散分布着细小的α-Al₂O₃颗粒;具有梯度热膨胀系数黏结层表面的热生长氧化物（TGO）生长速率显著低于传统黏结层,且不再遵循抛物线生长规律,而是以对数规律生长;由于生长速率缓慢,尽管在制备过程中消耗了部分Al元素,但在500 h范围内TGO仍然以α-Al₂O₃为主。 

High temperature oxidation behavior of double-layer bond coat in thermal barrier coating

High temperature oxidation behavior of( porosity layer + oxidation layer) double-layered bonding thermal barrier coat with gradient thermal expansion coefficient was studied in a box-type resistance furnace. The shrouded plasma spraying was employed to deposit a 60 μm thickness of porosity layer on Inconel 738 superalloy substrate,then an oxidation layer with thickness of 120 μm was sprayed on porosity layer via high-velocity oxygen fuel spraying( HVOF). The high temperature oxidation behavior of the double-layer bond coat was studied based on the different time at 1000 ℃. The results show that the as-sprayed porosity layer has a typical lamellar structure and no obvious oxidation. The as-sprayed oxidation layer contains some dispersive distributed α-Al2O3. The growth rate of thermally grown oxide( TGO) on bond coat with gradient thermal expansion coefficient is dramatically lower than that of traditional bond coat. The growth of TGO obeys logarithm law instead of parabola law. In spite of depletion of a fraction of Al element during deposition,the TGO is still dominated byα-Al2O3 within the range of 500 h due to the lower growth rate.