Reaction-Forming Method for Joining SiC-Based Parts

Two reports present additional details about the method described in "Reaction-Forming Method for Joining SiC-Based Ceramic Parts" (LEW-16661), NASA Tech Briefs, Vol. 23, No. 3 (March 1999), page 50. To recapitulate: A carbonaceous mixture (typically a paste) is applied to a joint between parts. The parts are clamped together and heated to a temperature of 115±5 °C for 10 to 20 minutes; this action partly cures the mixture, gluing the parts together with just enough strength that one need not clamp the parts during subsequent processing. Silicon or a silicon alloy in tape, paste, or slurry form is applied to the joint region. The parts are heated to a temperature between 1,250 and 1,425 °C for 5 to 10 minutes, causing the silicon or silicon alloy to melt, infiltrate the joint, and react with carbon. The finished joint, which is typically as strong as the parent material, contains silicon carbide with silicon and other phases. The amounts of the phases can be adjusted, by choice of the compositions of the reactants, to obtain joints with tailorable microstructures and thus tailorable thermomechanical properties.