Compared with other kinds of superalloys, high temperature niobium alloy has the advantages of low density, high temperature (600~1600 ℃) specific strength, good cold and hot forming performance, good welding performance, etc., can be processed to form thin-wall and complex shape parts. Thrust chamber body extensions for attitude control/orbit control engines for rocket engines, satellites, spacecraft and missiles are one of the important candidate materials for aerospace structural components.
In aerospace, China's most used is C-103 and Nb521 alloys, at present, orbit control/attitude control engine refractory metal material thrust chamber has formed a "two generation" series of products. Among them, the "first generation" is niobium hafnium alloy (i.e. C-103) and the "815" coating system, and the "second generation" is niobium tungsten alloy (i.e. Nb521) and the "056" coating system. The high temperature mechanical properties of Nb521 are much higher than C-103 alloy, and its strength is 3 to 4 times that of C-103 alloy at 1600 ℃, and it has been successfully applied to a variety of orbital control/attitude control engines.
C-103(Nb-10Hf-1Ti) alloy is a kind of low strength niobium alloy with good high temperature strength, excellent formability and weldability, which is widely used in rocket propulsion and other fields. In our country, the imitation of the alloy is applied to the two-component liquid rocket engine, and the niobium silicide high temperature anti-oxidation protection coating is used, and the working temperature can reach 1200~1300 ℃.
Nb521 niobium alloy has good room temperature formability, and can usually be used to fabricate a uniform transition nozzle extension section, but most of the nozzles are obtained by machining bars, which is difficult to machine and the material utilization rate is relatively low. Therefore, the study of near net forming and additive manufacturing of Nb521 niobium alloy is an effective method to improve the utilization rate of the alloy material.
In addition, the high temperature anti-oxidation coating of molybdenum silicide prepared in Nb521 alloy material has a certain self-healing ability, and the linear expansion coefficient of Nb521 alloy material is relatively close, so it has good anti-oxidation protection and binding properties.
