Coupled effects of temperature gradient and oxidation on thermal stress in thermal barrier coating system
Coupled effects of temperature gradient and oxidation on thermal stress in thermal barrier coating system
复制标题
DOI：
10.1016/s0020-7683(00)00309-7
复制
发表时间：
2001-06
影响因子：
3.6
通讯作者：
Yichun Zhou;T. Hashida
中科院分区：
文献类型：
--
作者：
Yichun Zhou;T. Hashida
本文研究了热障涂层（TBC）体系中的热应力场。热应力场是温度梯度、氧化、热疲劳、蠕变、TBC体系形貌和冷却速率等非线性耦合作用的结果。假定TBC体系是由8wt .%的Y2O3（PSZ）或莫来石组成的部分稳定的zro2，覆盖在镍高温合金或钢基体上的NiCrAlY结合涂层上。TBC体系是圆柱坐标系下的四层复合介质。采用泰勒变换和格林函数方法，对介质中具有能量产生的非齐次问题的温度场进行了解析求解。在考虑特征应变率的情况下，得到了复合介质热应力场的解析解。用通式给出了陶瓷涂层（PSZ和莫来石）和基体（ni -高温合金）的蠕变、结合层塑性等本构方程。考虑了热生长氧化（TGO）和热力学参数的温度依赖性。给出了温度场和热应力场的计算结果，并对相关结果进行了讨论。TGO不影响PSZ涂层系统的温度场。但它对莫来石涂层体系的温度场有影响。考虑TGO的残余应力大于未考虑TGO的残余应力。得出TGO可能使残余切向应力由拉向压的结论是非常有趣的。PSZ涂层体系的热应力表征与莫来石涂层体系的热应力表征有很大不同。这可能是由于其蠕变、热失配和力学失配等力学行为的差异，这些都反映在Dundurs参数α和β上。几何半径不仅影响热应力的量子化，而且影响热应力的表征。冷却速率对残余应力的影响是由于陶瓷涂层在高温下的高蠕变速率造成的。对于运行在相对低温下的系统，冷却速率对残余应力的影响不大。
The thermal stress fields in thermal barrier coating (TBC) system are studied in the present paper. The thermal stress fields are induced by the non-linear coupled effect of temperature gradient, oxidation, thermal fatigue, creep, morphology of TBC system as well as cooling rate. TBC system is assumed to be partially stabilized ZrO2by 8 wt.% Y2O3(PSZ) or mullite over a NiCrAlY bond coat sprayed on nickel superalloy or steel substrate. The TBC system is a composite medium with four layers in cylindrical coordinate system. The temperature fields for the non-homogeneous problem with energy generation in medium are analytical solved by using Taylor transformation and Green’s function approach. The analytical solutions for thermal stress fields in composite medium are obtained when eigenstrain rate is taken into consideration. The constitutive equations, such as the creep of ceramic coating (PSZ and mullite) and substrate (Ni-superalloy), plasticity of bond coat are given by a general formula. Thermal growth oxidation (TGO) and the temperature dependence of thermal–mechanical parameters are taken into consideration. The calculated results of temperature fields and thermal stresses fields are given and the related results are discussed. TGO does not affect the temperature fields in PSZ coating systems. But it has influence on temperature fields in mullite coating systems. The residual stress with TGO considered is larger than that with TGO non-considered. It is very interesting to have the conclusion that TGO may make the residual tangent stress from tensile to compressive. The characterization of thermal stresses in PSZ coating system is very different from that in mullite coating system. It may be due to the difference of mechanical behavior such as creep, thermal mismatch as well as mechanical mismatch which is reflected by Dundurs' parameters α and β . The geometrical radius not only affects the quantum of thermal stress but also affects the characterization of thermal stress. The effect of cooling rate on residual stress is due to the high creep rate of ceramic coating operating at high temperature. The effect of cooling rate on residual stress is not large for system operating at relative low temperature.