Effect of joint clearances on microstructure and property of brazed SiC ceramics

The effect of joint clearance on microstructures and property of SiC ceramics brazed with Ti-Zr-Ni-Cu brazing filler was studied by means of SEM, EDS and XRD.The joint microstructure from SiC ceramics to the center of brazing seam are TiC, Zr(s, s), Ti₅Si₃+Zr₂Si, Ti(s.s)+Ti₂(Cu, Ni) and(Ti, Zr)(Ni, Cu) successively.When the joint clearance is 30 μm~50 μm, Si reacts with Ti and Zr element, and produces a small quantity of tiny needlelike silicon compounds.Homogeneous solid solution is full of the brazed joint.The mechanical property is superior and the shear strength can reach 117 MPa.When the joint clearance is less than 30 μm, longstring silicon compounds are generated, and run through the brazing beam.Meanwhile, successive and thick TiC layer is produced.Both of these two factors lower the mechanical property.When the joint clearance is more than 50 μm, Ti-based intermetallic increases and eutectic compounds are produced, which reduce the mechanical property.