梯度层不同配比对等离子喷涂Mo/8YSZ功能梯度热障涂层残余应力的影响规律研究

Influence Rule of Different Ratios of Gradient Layer on Residual Stress of Plasma Sprayed Mo/8YSZ Functionally Graded Thermal Barrier Coating

传统的金属/陶瓷双层热障涂层因不同涂层热物性参数的差异,易在涂层内部产生过大的残余应力,影响涂层质量及可靠性,而采用梯度结构的热障涂层,可实现涂层厚度方向热物性参数的连续平滑过渡,从而减小涂层间的残余应力,提升涂层的可靠性。梯度层配比不同,将使得涂层残余应力的分布情况及数值大小不同,为了研究不同梯度层配比对Mo/8YSZ功能梯度热障涂层残余应力的影响规律,利用ANSYS有限元分析软件建立了等离子喷涂Mo/8YSZ双层热障涂层及功能梯度热障涂层的数值模型,并在模型中考虑了材料热物性参数随温度变化,对比传统双层热障涂层,分析了不同梯度层配比对喷涂构件残余应力数值大小及分布区域的影响规律。结果表明:在喷涂参数相同的情况下,功能梯度热障涂层系统相比于双层热障涂层系统,径向最大残余拉应力与压应力均增大,轴向最大残余应力减小;伴随着过渡层第一层Mo比例的增加,喷涂构件的最大轴向残余拉应力增大,喷涂构件的最大轴向残余压应力减小;伴随着过渡层第一层Mo含量的增大,基体与涂层界面拉应力的分布区域增大,压应力的分布区域减小;采用功能梯度热障涂层结构,由于缓和了不同种类涂层间热物性参数的差异,可显著改善喷涂构件轴向的应力突变情况。

The traditional "metal/ceramic" double-layer thermal barrier coating is prone to produce excessive residual stress inside the coating due to the difference in thermal and physical properties of different coatings, which will affect the quality and reliability of the coating. The thermal barrier coating with gradient structure can realize continuous and smooth transition of thermal property parameters in the direction of coating thickness, thus reducing residual stress between coatings and improving the reliability of coating. The distribution and numerical value of residual stress of coating are different with different ratio of gradient layer. In order to study the influence of different gradient layer ratio on the residual stress of Mo/8 YSZ functionally gradient thermal barrier coating, the numerical models of Mo/8 YSZ double-layer thermal barrier coating and functionally gradient thermal barrier coating with plasma spraying were established by using ANSYS finite element analysis software, and the variation of material thermal property parameters with temperature was considered in the model. Compared with traditional double layer thermal barrier coating, the influence of different gradient layer ratio on residual stress value and distribution area of spraying components was analyzed. The results showed that compared with the double-layer thermal barrier coating system, the maximum radial residual tensile stress and compressive stress increase, while the maximum axial residual stress decreases. With the increase of Mo ratio of the first layer of the transition layer, the maximum axial residual tensile stress of the spraying component increases, while the maximum axial residual compressive stress of the spraying component decreases. With the increase of Mo content in the first layer of the transition layer, the distribution area of tensile stress at the interface between substrate and coating increases, while the distribution area of compressive stress decreases. The functional gradient thermal barrier coating structure can significantly improve the axial stress mutation of spraying components because it eases the difference of thermal and physical properties among different coatings.