Effect of Ti addition on the wetting and brazing of Sn0.3Ag0.7Cu filler on SiC ceramic

The wetting behavior of Sn0.3Ag0.7Cu (SAC) filler with the addition of Ti on SiC ceramic was investigated using sessile drop method. SiC/SiC was brazed by SAC-Ti filler with different Ti content at 1223K (950 degrees C) for 10minutes. The wettability of SAC-Ti filler on SiC was significantly enhanced with the addition of Ti. The contact angle decreased at first and then increased with increasing Ti content. The lowest contact angle of 9 degrees was obtained with SAC-1.5Ti (wt%) filler. When Ti content further increased to 2.0wt%, the contact angle increased, due to the intense reaction of Ti-Sn. The reaction between Ti and SiC controlled the wetting behavior of SAC-Ti on the SiC substrate and the reaction products such as TiC and Ti5Si3 were formed. The wetting of SAC-Ti on SiC was reaction-controlled. Interfacial reaction products TiC and Ti5Si3 were observed. The wetting activation energy in spreading stage was calculated to be 129.3kJ/mol. Completely filled SiC/SiC joints were obtained using the filler with Ti content higher than 0.5wt%. The fillet height increased firstly then decreased with mounting Ti content. The shear strength of joints increased first with the addition of Ti then decreased with Ti content increasing to 2.0wt%. The highest shear strength of 35.7MPa was obtained with SAC-1.5 Ti (wt%) filler.