Microstructure Evolution and shear strength optimization in SiC ceramic/MA956 ODS steel joints brazed with Cu-Ti-Si filler

Brazing of SiC ceramic is of importance for its application, but the decomposition of SiC is harmful to the performance of SiC brazed joint. In our work, Cu-Ti-Si filler was designed to braze SiC ceramic and MA956 ODS steel. The effects of brazing temperature and holding time on the microstructure evolution and mechanical properties of the joints were investigated, and the microstructure evolution mechanism was explored. The joint fabricated at 960 °C for 10 min exhibited a typical interfacial microstructure consisting of SiC / Cu_6.69Si + graphite /TiC /Ti₅Si₃ /TiCuSi + Ti₅Si₃ + Cu(s,s) /TiCuSi + Cu(s,s) /TiFeSi + Cu(s,s) / MA956. Continuous layered decomposition products from SiC were exclusively observed at the maximum brazing temperature of 1020°C, compared to the Cu-5Ti filler without Si addition, a significant suppression of SiC decomposition was achieved, while holding time exhibited negligible influence on SiC decomposition extent. Both elevated brazing temperature and prolonged holding time significantly reduced the braze seam width. The shear strength of the joints originally increased and then decreased with rising brazing temperature. The maximum shear strength of 65 MPa was achieved at 960°C for 10 min, representing a 54.8 % enhancement compared to joints fabricated using Cu-5Ti fillers.