Plasma etching as a surface engineering technique for SiC/SiC composites to improve joint strength

Silicon carbide fiber reinforced silicon carbide (SiC/SiC) composites have unique properties that make them suitable for demanding applications. These materials have to be joined with other materials or with the same type of material to produce the final component. This work investigates the effectiveness of a fluorine-based plasma process on SiC/SiC composites as a surface engineering technique to manufacture a brush-like texturized surface. The studied pre-treatment induced an interlocking effect at the composite/joining material interface, thus improving the joint strength of the joined components. Several plasma conditions were considered and the most promising one (CF4, 20 sscm, 200 W, 30 min) was selected to assess the effect on the mechanical performance of SiC/SiC brazed with a commercial brazing alloy (Cusil-ABA®). The selected plasma pre-treatment led to a 55% increase in the apparent shear strength of the joined SiC/SiC composites.