Effect of graphite content on microstructure and properties of Al2O3 ceramic and 304 stainless steel brazed joints

Abstract Al2O3 ceramic and 304 stainless steel were brazed by Ag-Cu-Ti filler. Graphite was added into the Ag-Cu-Ti filler to improve the properties of the joint. The effects of graphite content on the microstructure and properties of Al2O3/304 joint were investigated. The microstructure of the joint was Al2O3/Cu3Ti3O + TiCu/Ag(s,s) + Cu(s,s) + TiC + TiCu/Cu0.8Fe0.2Ti/Fe-Cr/304. The shear strength was 130.54 MPa with Ag-Cu-Ti. When 0.1 wt% graphite was added, strength of joint reached 203.49 MPa. The improvement of shear strength was attributed to the formation of TiC, which reduced the coefficient of thermal expansion (CTE) difference and refined the microstructure. When the graphite content exceeded 0.2 wt%, graphite would agglomerate in the joint, which deteriorated the mechanical properties of the joint.