QT500表面等离子喷涂8YSZ热障涂层TGO的残余应力状态及数值分析

State of Residual Stress and Numerical Analysis of TGO in Plasma Sprayed 8YSZ Thermal Barrier Coating on QT500

分别采用超音速火焰喷涂（HOVF）和等离子喷涂（APS）在QT500球墨铸铁基体上制备Co Ni Cr Al Y粘结层（BC）和8YSZ陶瓷隔热层（TC）,研究了试样在1050℃高温环境中经过2.5、8、15、50、100 h恒温氧化后体系的应力情况。利用扫描电子显微镜（SEM）对热生长氧化物（TGO）的微观形貌进行观察与分析,并用拉曼荧光光谱仪（RFS）分析了其应力的分布及变化规律,并通过力学模型进行了残余应力的数值计算。结果表明：由陶瓷层与粘结层之间的热失配而导致TGO中产生残余压应力,其最大值范围为1.9557-1.9603 GPa;残余压应力在高温氧化初始阶段逐渐减小,至15 h达到最小值,随之逐渐增大后趋于稳定;在恒温阶段,θ-Al2O3转变为α-Al2O3所引起的体积收缩是TGO中残余应力减小并趋于稳定的直接原因。

CoNiCrA1Y bond coat and ZrO2-8wt%YzO3 （8YSZ） top coat were deposited on QT500 nodular cast iron by High Velocity Oxy-fuel （HVOF） and Air Plasma Spraying （APS） processes, respectively. The sprayed samples were heat treated in a furnace at 1050 ℃ for 2.5, 8, 15, 50 and 100 h. Afterwards, the growth of Thermally Grown Oxide （TGO） was observed by SEM and the variation of TGO stress was analyzed by Raman Fluorescence Spectrometer. A numerical model was established to evaluate the stress distribution in the TGO. Results show that TGO was in a compressive stress state, which was derived from thermal mismatch between bond coat and top coat. The highest residual stress in the TGO ranged from 1.9557 to 1.9603 GPa, which decreased gradually at the initial stage, and then reached its minimum at 15 h, but increased to a constant value in the latter stage. The volume contraction caused by the process of 0-A1203 to a-A1203 phase transformation is a dominant factor for the TGO residual stress variation.