Interfacial Microstructure and Mechanical Properties of Pressureless Sintered SiC Ceramic and Stainless Steel Joints Brazed by AgCu/AgCuTi Alloy

A high-quality joint of pressureless sintered SiC ceramic (PS-SiC) and stainless steel brazed by AgCu/AgCuTi brazing alloy was realized. The effects of brazing temperature and holding time on the interfacial microstructure and mechanical properties of PS-SiC-stainless steel were analyzed. During brazing, Fe and Cr diffused into a brazing seam, and the typical interfacial microstructure of joints brazed at 890 °C for 15 min was stainless steel/Cr5Si3 + FeSi2 + Ag(s,s)/Cr5Si3 + FeSi2 + Ag(s,s) + Cu(s,s) + TiSi2 + TiC/FeSi2 + Ag(s,s) + Cu(s,s) + TiSi2/Ag(s,s) + Cu(s,s) + SiC/PS-SiC ceramic. Cu-Fe system improved the toughness of the joint, and the shear strength of the joint increased to ~67 MPa. With increasing brazing temperature and holding time, the element Fe continued diffusing into the brazing seam, and the uniformity of Cu-Fe system became worse. Then Cu(s,s) infiltrated into the surface layer of PS-SiC ceramic and FeSi2 brittle phase gathered in the brazing seam. Then, the brittleness of the joint increased and the shear strength of the joint decreased.