Residual Stress Analysis of Ceramic Thermal Barrier Coating Based on Thermal Spray Process

Abstract

Residual stress is generated in ceramic thermal barrier coatings (TBCs), which were sprayed by a plasma spray technology, due to the difference in coefficients of thermal expansion between the coating and the substrate. Previous experimental results obtained by the X-ray diffraction method indicated that the residual stress at the ceramic coating surface is tensile and could lead to TBC failure such as cracking and spalling of the ceramic coating. In this study, a numerical model that can predict the residual stress exactly is proposed by taking into account a thermal spray process. This numerical model is a layer-buildup model based on a shear-lag theory, and the residual stress contribution comes from two kinds of the following stress components: (1) quenching stress, which was generated in molten spray particles impinged onto the substrate, and (2) thermal stress, which was generated due to differences in thermal expansion between the deposited particle and the underlying substrate. It is shown herein that residual stress predicted by the proposed numerical model coincided with the experimental one obtained by the strain gage technique, with a good level of accuracy.

High Temperature Long-term Service Performance of TiAlCrY/YSZ Coating on TiAl Alloy

“…一般地, Ni 基高温合金表面热障涂层失效主要 是由应力造成的, 可归结为三种情况 [25][26][27] 表面 NiCrAlY/YSZ 体系中, TGO 的厚度一般要求控 制在<8 μm 的范围内 [18,28] 11.3×10 -6 ~17.3×10 -6 和 13.0×10 -6 ~26.0×10 -6 K -1 [29] 范 围 , 在 热 冲 击 过 程 中 会 产 生 拉 应 力 [30] 。 其 中 , TiAlCrY 的热膨胀系数约为 NiCrAlY 的 67%~87%, 产生的拉应力也小于 NiCrAlY 涂层。一般来说, 涂 层内适当存在的压应力有利于抑制裂纹扩展, 因此, 在 TiAlCrY/YSZ 涂层的高温服役性能测试过程中, YSZ 涂层几乎无明显的剥落现象 [13] 。而涂层内的拉 应力会加速涂层内部裂纹扩展, 不利于延长涂层的 服役寿命 [31]…”

Running-in behaviour of thermal barrier coatings in the combustion chamber of a diesel engine

“…By using finite element modelling, the risk of forming cracks, such as those found in the YSZ and GZ coatings, can be evaluated. Numerical models predicting the residual stresses from the plasma spraying process has been developed by different researchers, 40,41 and others have also included mechanical and thermal loads to describe the stresses and fracture mechanics of pistons with TBCs. 42 These finite element models, as well as in-situ heat flux measurements with a heat flux probe, such as the one presented in this article, are both valuable tools for developing improved TBCs for diesel engines.…”

Inelastic deformation behavior of thermal barrier coatings exposed at a high-temperature environment

“…TBCs are generally deposited using a plasma-spray technique. This deposition technology is known as a mechanical process impacting and depositing continuously particles molten into a plasma hightemperature flow onto a target surface [1]. Thus, a stress-strain curve as one of the mechanical properties of the ceramic coating in TBCs is affected strongly by the deposition parameter.…”