Multialloying effect on thermophysical properties of Cr7C3-type carbides

The alloying element effect on the thermophysical properties of Cr7C3-type ceramics is essential for the applications. The thermal expansion for these compounds is calculated using quasi-harmonic approximation combined with density functional theory. The linear expansion coefficient along [100] direction is larger than that along [010] and [001] direction. The B- and Mo-codoped Fe4Cr3C3 has the smallest thermal expansion coefficient. We obtained the temperature dependence of bulk modulus, pressure derivative modulus, and the Gruneisen constants. Furthermore, we propose a new method to calculate the anisotropy of minimum thermal conductivity which is suitable to the large complex unit cells. The three-dimensional (3D) expression of anisotropy of minimum thermal conductivity are presented companied with planar projections on (100), (010), (001), and (110) crystal planes. The minimum thermal conductivity of Fe3Cr3WC2B is lower than other multicomponent compounds. The charge density differences and chemical bonding between Mo/W and B are found to be the key factor on the thermophysical properties of these compounds.