Study On Joining Method Between Re Thrust Chamer And Injector Of Attitude/Orbit Control Rocket Engine

High-performance Rhenium/Iridium chamber applied in the liquid engine for attitude and orbit control has the properties of high temperature,high specific impulse and long life,and the key technology of the engineering applications of Re/Ir thrust chamber is to achieve reliable joining of Re substrate and titanium alloy injector.Technologies of directly brazing Re substrate to the TC4 injector,and brazing Re substrate to the Nb injector transition can meet the requirements of applying under different temperatures.In this paper,Re/TC4 and Re/Nb joints were successfully obtained by the vacuum brazing method,and the microstructure and mechanical properties of the joints were investigated by SEM,EDS and shear strength tests respectively.Also,the Re/Ir chamber was also brazed to the TC4 or Nb transition.The brazing of Re and TC4 was carried out with TiZrCuNi amorphous braze fillers,and the effect of brazing parameters on the microstructure and mechanical property were studied.The interface microstructure of Re/TC4 joints is Re/diffused solution layer/primary?(Ti)+intermetallic compounds/eutectoid microstructure+intermetallic compounds/TC4.The maximum ambient temperature shear strength of 205MPa was achieved with the brazing temperature of 910~oC,holding time of 10min,and 8 layers brazing foils.The high temperature(400-600~oC)and the room temperature shear strength basically remain the same.The fracture of the joints occurs at the interface between diffused solution layer and the brazed seam microstructure,and the fracture mode is brittle fracture.Brazing of Re and Nb joint using Ti-Ni fillers was also performed,and the results showed that the mechanical properties of the joint were mainly affected by the growth of(Nb)grains and the precipation of intermetallic compounds.The interface microstructure of Re and Nb can be simply expressed as Re/(Nb)solution/intermetallic compounds/(Nb)solution/Nb.The shear strength decreases with the increase of brazing temperature and holding time.The joint strength was 261MPa at the brazing temperature of 1160 ~oC and holding time of 10min.The mechanical properties of the joint at 1000 ~oC reached 75MPa,which exceeded 34%of the strength of Nb base metal.The fracture of the joint occurs at the intermetallic compound layer in the center of the seam,and the cleavage fracture and intergranular fracture are the main types,representing brittle fracture mode.The joining of Re/Ir chamber to TC4 and Nb injector transition section was carried out.The results showed that the joints of Re/Ir chamber and TC4 or Nb transition could be successfully obtained with the optimized brazing technologies.The Re/TC4connection joint was sucessfully achieved without observation of welding decfect of leak,crack and hole,while several microdefects were observed in the Re/Nb connection joint.The pressure resistant property of the connection joint was tested,and the results showed that the joints has an excellent air tightness property.In addition,aiming at the issue of joining Rhenium/Iridium/C-C composites chamber to titanium alloy injector,the preparation of Rhenium metallic coating on C-C composites substrate was studied,and the preliminary research of brazing Re metallic coated C-C to the TC4 was also conducted.