Atmospheric Pressure Plasma Jet for Surface Texturing of C/SiC

C/SiC composites are materials to be used in harsh environments overcoming the limits imposed by the intrinsic brittleness of their ceramic constituents while providing both high mechanical performances at high-temperature temperatures and low weight. In order to manufacture the final component, joining C/SiC, to itself or to other materials, is often necessary, and it is critical to maximize the strength of the joints (similar or dissimilar) in order to meet reliability criteria. In the present work, a pre-joining treatment based on an atmospheric pressure plasma jet (APPJ) was proposed to introduce a brush-like texture on the surface via the selective removal of carbon fibers. The investigation of treated surfaces via electron microscopy and confocal 3D-profilometry confirmed that the treatment was effective in introducing a brush-like texture and in increasing the available contact area. Wettability test and inspection of cross-section of CB4 wetted samples were then carried out. The latter confirmed the formation of anchoring points given by the brush-like texture. Finally, the effectiveness of the treatment in improving the joint strength was assessed by comparing the apparent shear strength of CB4 brazed composites, with and without the APPJ pre-treatment. The joints with plasma pre-treated C/SiC showed a shear strength of about 66 MPa, 44% more than the strength of joints produced with untreated C/SiC.