Plasma etching of SiC/SiC composites to improve joint strength

Ceramic matrix composites (CMCs) offer unique properties to address harsh environments because of their high-temperature mechanical behavior and chemical resistance. To manufacture the final component, parts made of CMCs usually have to be integrated with other materials or with themselves by joining. A sound joint is vital for providing a solution for the targeted application. To this end, surface preparation is a key step to enable the formation of a strong interface between the joining material and the part to be joined. In particular, a texturized surface can provide mechanical anchoring points between the adhesive and the underlying material, resulting in higher mechanical resistance of the joint[1]. Among the viable textures, a brush-like one is of particular interest to improve the interlocking effect in joining CMCs[2]. In this work, 2D SiC/SiC composites were etched via a fluorine-based plasma process to provide a brush-like texturized surface as a result of the differential etching experienced by the matrix and the fibers. A similar treatment was successfully proposed for surface modification of bulk SiC in previous work[3]. Then, several plasma conditions were tested, and one was selected as suitable. Finally, the plasma-etched SiC/SiC and the untreated SiC/SiC were joined using a brazing alloy and they were mechanical tested to assess the effectiveness of the treatment in enhancing the joint strength. The results of the activity are presented.