Reactive pressure infiltration of Cu-46at.pct. Si into carbon

Abstract

We explore how reaction at the interface between a solid porous ceramic and an infiltrating molten metal influences wetting in pressure infiltration, wetting being characterized by a drainage curve that plots the metal saturation versus the applied metal pressure. Specifically, we infiltrate Cu-46at.pct. Si into graphite preforms at 1050 °C, 1100 °C, 1150 °C or 1200 °C. The Si in the copper alloy reacts with the graphite to form SiC, which is better wetted by the alloy compared to the initial graphite. We show that, unlike what is observed in non-reactive systems, at fixed applied pressure reaction prevents stabilization of the metal saturation and causes the metal to continuously flow into the preform. Interpreting the data under the assumption that the applied pressure influences the local rate of thermally activated triple line motion as does the applied stress the rate of thermally activated motion of dislocations, measured infiltration velocities can be exploited to deduce both an activation volume and an activation energy for the interfacial process that governs reaction-driven motion of the triple line in this system. The resulting activation volume is on the order of one to a few 100 nm3, leading to estimated activation energy values of a few times 100 kJmol. Both are realistic for a process that is limited by the rate of SiC growth along the metal/graphite interface.