Spacecraft engine is mainly used in launch vehicles, satellites and spacecraft, is a highly complex and precise thermal machinery, to provide flight power for spacecraft, can directly affect the performance of spacecraft, reliability and economy. In order to ensure that the spacecraft engine components have a certain service life, it is required that the material must meet the full high and low temperature mechanical properties, good thermal corrosion properties and high temperature oxidation resistance. With the rapid development of space exploration technology, the thrust-to-weight ratio of the engine is getting higher and higher, and the working temperature is also significantly increased, so it is imperative to develop ultra-high temperature alloy materials with excellent high temperature mechanical properties, thermal strength and high temperature oxidation resistance.
Niobium (Nb) is a refractory metal of the VB group, melting point 2468℃, bcc structure, thermal expansion coefficient of 7.2×10-6 K-1, density similar to steel, 8.56 g.A-M-3, strength can be maintained to 1649.90℃, and can withstand certain mechanical deformation. The pure metal niobium has high solid solubility for many strengthening elements such as W, Mo, Zr and so on. Based on its superior physical and chemical properties, niobium alloy can be used as the main choice of ultra-high temperature alloy materials for aircraft engines. However, niobium alloy at 600-8000C, the phenomenon of pest oxidation (pest) IS, with the thickening of the oxide layer, the internal stress generated at the interface between the oxide and the metal can crack the oxide layer, followed by catastrophic oxidation, so it is necessary to use a coating matching with niobium alloy to improve its high-temperature oxidation resistance. The niobium base alloy mainly used for aerospace vehicle orbit control and attitude control engine is C103 alloy developed by the United States (the main composition is 10Hf-1Ti-0.5Zr, the rest is niobium) and the coating prepared by slurry sintering method and C103 alloy matching, the main temperature range is 1200-1400℃. Due to the limitation of applicable temperature, high temperature mechanical properties and thermal strength, niobium base alloy C103 and its coating can not meet the needs of spacecraft. Therefore, it is of great significance to prepare a new niobium base alloy with excellent high temperature mechanical properties and thermal strength and its matching high temperature oxidation resistant coating. The new niobium-tungsten alloy Nb521-1 and its supporting coating prepared in this paper have been successfully applied to the nozzle of the gas-oxygen kerosene engine of the new generation of high-thrust non-toxic launch vehicle, four attitude orbit control engines such as Sinosat 6 and Nigeria Satellite, and the engine of the Chinese Lunar rover project.
