椭球形陶瓷颗粒增强镍基合金复合涂层热膨胀系数预报

Thermal expansion coefficient prediction of ceramic particle reinforced Ni base alloy coating

陶瓷颗粒增强镍基合金复合涂层在各种高温环境下被大量应用,因此关于此类材料的线热膨胀系数预报与研究是十分重要的。研究把涂层简化为三相模型,碳化铬陶瓷粒子和基体壳简化为椭球形二相胞元,用Eshelby-Mori-Tanaka法研究了二相胞元的热失配等效本征应变和平均应变,根据平均应变算出了二相胞元的线膨胀系数,结果表明,二相胞元为横观各向同性,具有2个独立的热膨胀常数。据二相胞元方位的随机性,由应力应变换轴公式和物理方程确定了复合涂层的平均应变,进而得到复合涂层的热膨胀系数。

Ni base alloy ceramic composite coating is used mostly in high temperature condition, so the prediction and study of its thermal expansion coefficient is very important. In this paper, we regard that the coating is composed of effective medium, ceramic particles and Ni matrix around each particle. The ceramic particle and the Ni matrix around it is called two phase model. The Eshebly-Mori-Tanaka method is introduced to study the eigen strain and even strain of the two phase model, then the thermal expansion coefficient of the two phase model is gotten according to the even strain. Form the results we know the two phase model is transverse isotropy and has two independent thermal expansion coefficients. The ceramic particles are oriented randomly in the coating, and we can get the even strain of the coating through choosing an appropriate distributing function, at last the thermal expansion coefficient of the coating is gotten.