梯度热障涂层的设计

DESIGN OF GRADIENT THERMAL BARRIER COATINGS

采用电子束物理气相沉积方法 (EB PVD)制备了梯度热障涂层 ,其结构设计为NiCoCrAlY粘结层 /Al2 O3 YSZ过渡层 /YSZ陶瓷层。YSZ陶瓷层的结构为柱状晶结构 ,Al2 O3 YSZ梯度过渡层为梯度微孔结构。采用有限元方法对梯度热障涂层进行热应力分析 ,优化了Al2 O3 YSZ梯度过渡层的组成。计算结果表明 ,梯度涂层的内应力显著降低 ,而且界面及其附近应力和应变变化较平缓。过渡层厚度的增加有利于降低涂层内应力和缓和涂层界面处的应力集中。

Gradient thermal barrier coatings (GTBCs) were prepared by co-deposition of a tablet of mixtures of AlAl2O3-YSZ and YSZ onto NiCoCrAlY bond coat by means of electron beam physical vapor deposition (EB-PVD). It was found that the microstructure is gradually transferred from metallic bond coat to YSZ topcoat and the composition distribution changes continuously with respect to the thickness of the coating. The coating exhibits a good resistance not only to high temperature oxidation but also to cyclic corrosion. A finite element numerical model was employed to study the stress developed in the coating during cooling. The results demonstrate that the Al2O3-YSZ graded layer provides a great reduction in the stress and stress gradient. The gradient layer is the crucial location that determines the lifetime of the gradient coating. The Al2O3-YSZ coating exhibited a lower thermal conductivity than traditional YSZ coating, which is caused by the microporous microstructure and the vacancies appearing in the ZrO2 lattice.