Spontaneous infiltration of iron silicides into silicon carbide powder preforms

The infiltration of liquid Fe,Si (mp of similar to 1300 degreesC), Fe,Si, ( mp of similar to 1210 degreesC), and FeSi (mp of similar to 1410 degreesC) into SiC powder preforms was performed at various infiltration temperatures for 60 min under either argon flow or dynamic vacuum, The amount of infilt ration under various infiltration conditions was studied as a function of i nfiltration temperature. For the preforms as-pressed from raw SiC powder, t he amount of infiltration of the three silicides under argon flow was indep endent of their melting points, but suddenly increased within a common temp erature range from 1450 degrees to 1550 degreesC, Thermodynamic analyses in dicated that the common temperature range corresponded to the temperature a t which the SiO2 on the surface of the SIC particles was decreased under ar gon flow. Infrared spectroscopy showed SiO2 on the surfaces of as-received SLC powder particles, but not on the surfaces of the SLC powder particles f ired under argon at 1600 degreesC, The amount of infiltration of the as-pre ssed SiC under vacuum and of fired SIC under argon and vacuum exhibited an obvious dependence on the silicide melting points. This was attributed to t he SiO2 reduction taking place at temperatures lower than the melting point s of the silicides, The amount of infiltration was then controlled by the m elt viscosity.