Study On The Bonding Process And Properties Of C_f/SiC Composites With Niobium

The rocket engine nozzle is the critical component of engine,accounts for about 20%?30%of the whole engine noble quality.Cf/SiC composite have the low density,good mechanical properties,high temperature resistant,ablation resistance and scour resistance,it can be worked long hours on 1923 K,worked some hours in 1923?2473 K,worked tens of seconds on 2473?3073 K.Therefore,The rocket engine nozzle is manufactureed using Cf/SiC composite,It is beneficial to reduce engine weight,and improve the life of engine thrust chamber sages and thrust weight ratio.It is more different on property between Cf/SiC composite and metal.The joint property need to be further improved by the existing jointed method.Therefore,It is the major problem on Cf/SiC composite applications that studying new connection technology between Cf/SiC composites and metal,and making performance reliable joint.In the present study,The Nb were deposited on Cf/SiC composite substrates by Chemical Vapor Deposition process using metal niobium(Nb)hydrogen and chlorine gas as starting materials,and obtain Nb-Cf/SiC composite joint.we investigate the hydrogen flow rate,chlorine flow rate and deposition temperature how to impact the deposition quality of Nb and deposition rate,and study interface structure and mechanical properties of Nb-Cf/SiC composite joint.Study the heat treatment process how to influence Nb-Cf/SiC composites joint interface reaction and interface bonding strength by heat treatment.OM,XRD,SEM and EDS are employed to characterize the Nb-Cf/SiC composites joint such as phase analysis,morphology observation and elements line scanning analysis of interface,The shear strength test is used for measuring the interface bonding strength of Nb-Cf/SiC composites joint.Metallographic analysis:Nb grow columnar crystal along the sedimentary direction.Increasing the gas flow rate,the deposition rate of niobium is greater and the grain size of Nb is more coarse;As the deposition temperature increase,the deposition rate of niobium is greater and the grain size of niobium more coarse.The XRD results show that the interface reaction of sedimentary state joint generates NbC,Nb3Si and Nb5Si3 phase.With the increase of heat treatment temperature,interface reaction further proceed,in addition to the NbC,Nb3Si and Nb5Si3 phase,also a new phase Nb2C is generate.The strength of joint results indicate that the shear strength of sedimentary state Nb-Cf/SiC composites joint is 21.73 MPa at room temperature.The shear strength of Nb-Cf/SiC composites joint reduce increasing heat treatment temperature at room temperature.There is the highest room temperature shear strength at T2 + 200? of heat treatment temperature,it is 37.75 MPa.As heat treatment time prolonged,the shear strength of Nb-Cf/SiC composites joint decreases at room temperature,when the heat treatment temperature isT2+200?,the shear strength at room temperature is the highest.The interface of Nb-Cf/SiC composite joint belong to metallurgical bonding by Chemical Vapor Veposition.The joint strength is higher.