Effect of Liquid-phase Siliconizing Process on Silicon Diffusion Behavior in Mo Matrix

Abstract

AbstractMoSi2 functionally graded coating on Mo substrate is prepared by liquid-phase siliconizing technology. The SEM, GDS and XRD analysis shows that the silicon content in gradient layer appears in three changing regularities. Along the Mo substrate to the surface of the coating, the phase composition of gradient coating changes as follows: Mo → transition layer Mo (main phase) + Mo3Si + Mo5Si3 → intermediate layer MoSi2 → surface layer MoSi2 (main phase) + Si. According to the Si-Mo diffusion couple and Arrhenius equation, the activation energy (Q) was obtained as 430 kJ·mol−1, and the Arrhenius dependence of D on temperature can be described as D = 4.9 × 10−3 exp(−430000/RT) m2/s. The diffusion temperature has an important influence on silicon diffusion coefficient. As the diffusion temperature increases, silicon diffusion coefficient is also gradually increasing.