Interfacial microstructure and mechanical properties of C/C composites and Nb joints brazed with Cu75Pt25 filler metal

C/C composites were successfully brazed to Nb substrate using Cu75Pt25 filler metal. The typical interfacial microstructure of brazed joints was C/C composites/NbC/Nb(s, s)/Cu(s, s)/NbPt2/Nb3Pt/Nb(s, s)/Nb. The effect of brazing temperature on the interfacial microstructure and joints properties were investigated in details. With the increase of temperature, the Nb-Pt reaction layer thickened and the thickness of brazing seam declined. The thickness of Nb(s, s) layer at C/C composites side increased gradually with the increase of temperature and then declined when brazing temperature was over 1160 °C. The optimal average shear strength of 26.7 MPa at room temperature and highest shear strength of 17.6 MPa at 600 °C were obtained when the joints were brazed at 1160 °C for 20 min.