Spontaneous Infiltration of Iron Silicides into Silicon Carbide Powder Preforms

Abstract

The infiltration of liquid Fe3Si (mp of ∼1300°C), Fe5Si3 (mp of ∼1210°C), and FeSi (mp of ∼1410°C) into SiC powder preforms was performed at various infiltration temperatures for 60 min under either argon flow or dynamic vacuum. The amount of infiltration under various infiltration conditions was studied as a function of infiltration temperature. For the preforms as‐pressed from raw SiC powder, the amount of infiltration of the three silicides under argon flow was independent of their melting points, but suddenly increased within a common temperature range from 1450° to 1550°C. Thermodynamic analyses indicated that the common temperature range corresponded to the temperature at which the SiO2 on the surface of the SiC particles was decreased under argon flow. Infrared spectroscopy showed SiO2 on the surfaces of as‐received SiC powder particles, but not on the surfaces of the SiC powder particles fired under argon at 1600°C. The amount of infiltration of the as‐pressed SiC under vacuum and of fired SiC under argon and vacuum exhibited an obvious dependence on the silicide melting points. This was attributed to the SiO2 reduction taking place at temperatures lower than the melting points of the silicides. The amount of infiltration was then controlled by the melt viscosity.