Interface Optimization And Mechanical Properties Of C/C Composite And Nb Brazed Joint

C/C composite is often used as high-temperature structural materials in the aerospace industry due to its low density,high specific strength and excellent high-temperature performance.In the actual application,due to the poor processing performance of C/C composite,it is often necessary to connect it with high temperature metals such as Nb and the commonly used method is active brazing.However,there is often high residual stress in the joints,which results in low strength,and the brazed joints have poor high temperature mechanical properties.In this paper,the C/C composites were electrophoretic depositing with SiC nanowires,and then were brazed to Nb with AgCuTi and TiZrNiCu respectively.When brazed with TiZrNiCu,the joints were optimized by adding interlayer.When the C/C composite and Nb were brazed with AgCuTi,the typical interface structure of the joints was:C/C composite/TiC/Ti₃Cu₄/Ag（s,s）+Cu（s,s）/TiCu/Nb.The joint was weakened because of a continuous Ti₃Cu₄ layer.In this paper,SiC nanowires were introduced by electrophoretic deposition to improve the wettability of the AgCuTi alloy and the joint’s interfacial structure.The effects of SiC nanowires on the interfacial interface structure were studied.When the deposition time was 30s,the joint had the highest room temperature shear strength of 48 MPa.On this basis,the effects of brazing temperature on the microstructure and the mechanical properties of the joint were studied.The high temperature shear test showed that the joint brazed with AgCuTi was obviously weakened under high temperature conditions.In order to improve the mechanical properties of the brazed joints at high temperature,the C/C composite and Nb were brazed with TiZrNiCu.The effects of the addition of Cu interlayer and its morphology on the interfacial microstructure and mechanical properties of the joint were studied.When the brazing parameter was900°C/5min the typical interfacial structure of the joint was C/C composite/（Ti,Zr）C/Ti（s,s）+（Ti,Zr）₂（Cu,Ni）/β-Ti/Nb.When a Cu foam interlayer was added,the typical interfacial structure changed significantly.The matrix phase was（Ti,Zr）（Cu,Ni）,in which the bulk structure of Ti₂Cu+Ni₁₁Zr₉ phase coated Ti₂Cu+Ni₁₀Zr₇phase and Cu₅₁Zr₁₄ phase were distributed in it.The addition of the Cu foam increased the shear strength of the C/C-TiZrNiCu-Nb joint at room temperature from15MPa to35 MPa.With the increasing of brazing temperature and the prolonging of holding time,the shear strength of the C/C-TiZrNiCu-Cu foam-Nb joint increased first and then decreased.When the brazing parameter was 900°C/5min,the joint had the highest shear strength.When the test temperature was raised to 600°C,the mechanical properties of the joint were basically unchanged.At this circumstance,the shear strength of the joint brazed with TiZrNiCu was much higher than that of the joint brazed with AgCuTi.