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Due to limitations in operating temperature and high-temperature mechanical properties, C-103 alloy and niobium silicide anti-oxidation coatings have been unable to meet the evolving needs of spacecraft. To this end, our country has developed Nb521 (Nb-5W-2Mo-1Zr) niobium alloy based on the Soviet 5ΒΜЦ niobium alloy. The alloy uses a high-temperature anti-oxidation protective coating of molybdenum silicide, which increases the operating temperature to about 1550°C, significantly reducing the flow rate used to cool the propellant in the combustion chamber, thereby effectively increasing the specific impulse of the engine and becoming China’s current orbit control system. The second generation niobium alloy base material for the thrust chamber of attitude control engine refractory metal material. Nb521 niobium alloy adds W, Mo, Zr alloying elements and a small amount of C element to the niobium matrix. It further improves the room temperature and high temperature mechanical properties of the niobium alloy through a combination of solid solution strengthening and precipitation strengthening. It is a medium-grade niobium alloy. Strength plastic niobium alloy. The alloy can be cast into ingots through vacuum electron beam melting or vacuum electron beam + vacuum consumable melting, and can be used to prepare rods, forgings and plates of various specifications through hot extrusion, forging, cold forging, drawing and rolling. W and Mo elements are added to the alloy mainly because of their high melting point and similar atomic radii, which can form a substitutional solid solution to improve the creep resistance and high-temperature strength of the alloy matrix.

Zr and C elements are added to the alloy because C easily forms a dispersed and precipitated strengthening phase with Zr and Nb, which plays a role in precipitation strengthening and can further improve the high-temperature strength of the alloy. Usually, dispersion strengthening of niobium alloys is strengthened through stable, fine carbides, oxides and nitrides. This strengthening method is very effective in improving high temperature strength.

Nb521 niobium alloy has good room temperature formability. Plate spinning can usually be used to prepare uniform transition nozzle extensions. However, most nozzles are obtained by machining from rods. The machining is difficult and the material utilization rate is low. relatively low.

The supporting high-temperature anti-oxidation coating has been successfully used in projects such as the nozzle of the gas-oxygen-kerosene engine of the new-generation high-thrust launch vehicle, satellites, Sino-6 attitude control/orbit control engines, and the Chinese lunar rover engine. It is the current domestic attitude control / the preferred material for the thrust chamber of orbital control engines is refractory metal materials.