By coating active titanium, Sn0.3Ag0.7Cu (SAC) filler wetted SiC effectively, as the contact angle decreased significantly from ~145° to ~10°. Ti3SiC2 and TiOx (x ≤ 1) reaction layers were formed at the droplet/SiC interface, leading to the reduction of contact angle. Reliable brazing of SiC was achieved using titanium deposition at 900°C for 10 minutes, and the typical interfacial microstructure of Ti‐coated SiC/SAC was SiC/TiOx + Ti3SiC2/Sn(s,s). Comparing to direct brazing, Ti–Sn compounds in the brazing seam were effectively reduced and the mechanical property of joints was dramatically improved by titanium coating. The optimal average shear strength of SiC joints reached 25.3 MPa using titanium coating‐ assisted brazing, which was ∼62% higher than that of SiC brazed joints using SAC‐Ti filler directly.
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 1223 K (950°C) for 10 minutes. 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° was obtained with SAC‐1.5Ti (wt%) filler. When Ti content further increased to 2.0 wt%, 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 129.3 kJ/mol. Completely filled SiC/SiC joints were obtained using the filler with Ti content higher than 0.5 wt%. 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 2.0 wt%. The highest shear strength of 35.7 MPa was obtained with SAC‐1.5 Ti (wt%) filler.
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