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The sintering behavior of plasma-sprayed YSZ coating over the delamination crack in low temperature environment
Ceramics International ( IF 5.2 ) Pub Date : 2018-02-01 , DOI: 10.1016/j.ceramint.2017.11.113
Hui Dong , Jian-Tao Yao , Xiao Li , Yong Zhou , Yuan-Bo Li

Abstract The sintering behavior of plasma-sprayed yttria-stabilized zirconia (YSZ) coating over the delamination crack and its influence on YSZ cracking were investigated via gradient thermal cycling test and finite element model (FEM). The gradient thermal cycling test was performed at a peak surface temperature of 1150 °C with a duration of 240 s for each cycle. A three-dimensional model including delamination cracks with different lengths was employed to elaborate the temperature evolution characteristics in YSZ coating over the delamination cracks. The temperature over the delamination crack increases linearly with the crack propagation, which continuously promotes the sintering of YSZ coating in the region. As a result, the YSZ coating over the delamination crack sinters dramatically despite of the low temperature exposure. Meanwhile, the temperature distribution difference in YSZ coating induces an nonuniform sintering along both free surface and thickness of YSZ coating. Correspondingly, the maximum vertical crack driving force locates at the YSZ free surface over the delamination crack center, which makes the vertical cracks generate in this region and propagate to the interface of YSZ /bond coat with YSZ further sintering. The vertical crack promotes the delamination crack propagation via accelerating the oxidation velocity of the bond coat. The influence of temperature rise on delamination crack propagation can be divided into two stages: the little contribution stage and the promotion stage. For the actual engine exposure to low temperature, the study of phase transformation of YSZ over the delamination crack is indeed needed because of an extended remarkable temperature rise period.

中文翻译:

低温环境下等离子喷涂YSZ涂层在分层裂纹上的烧结行为

摘要 通过梯度热循环试验和有限元模型(FEM)研究了等离子喷涂氧化钇稳定氧化锆(YSZ)涂层在分层裂纹上的烧结行为及其对YSZ裂纹的影响。梯度热循环试验在 1150 ℃的峰值表面温度下进行,每个循环的持续时间为 240 s。采用包含不同长度分层裂纹的三维模型来阐述YSZ涂层在分层裂纹上的温度演化特征。分层裂纹上方的温度随裂纹扩展呈线性上升,不断促进该区域YSZ涂层的烧结。结果,尽管暴露在低温下,分层裂纹上的 YSZ 涂层仍会显着烧结。同时,YSZ 涂层中的温度分布差异导致沿 YSZ 涂层的自由表面和厚度的不均匀烧结。相应地,最大垂直裂纹驱动力位于分层裂纹中心上方的YSZ自由表面,这使得垂直裂纹在该区域产生并随着YSZ进一步烧结而扩展到YSZ/结合涂层的界面。垂直裂纹通过加速粘结层的氧化速度促进分层裂纹扩展。温升对分层裂纹扩展的影响可分为两个阶段:小贡献阶段和促进阶段。对于实际暴露于低温的发动机,
更新日期:2018-02-01
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