稀土钨电极在电推进系统中的耐烧蚀性能研究

Research on Erosion Resistance of Rare Earth Tungsten Electrode in Electric Propulsion

阴极作为电弧加热发动机的“心脏”,担负着加热工质气体产生推进力的作用,由于卫星服役周期长,点火次数频繁,对阴极材料的寿命及耐烧损性能提出了很高的要求。为寻求耐烧损性能优异的阴极材料,以W-La-Ce-Y与W-La-Y-Zr电极为基础,采用氢还原-中频烧结的方法制备W-La-Ce-Y-Re与W-La-Y-Zr-Re电极材料。模拟发动机实际工况在250 A电流下进行燃弧试验,测量燃弧后电极的质量损失并对电极尖端的组织形貌进行观察。结果表明,加铼电极在燃弧2 h后的烧损质量更少,尖端形貌变化程度更小,耐烧损性能更好。在扫描电镜下观察到铼的加入抑制了尖端表面枝晶的生长,弱化了钨基体晶粒的再结晶程度,并探讨了稀土氧化物的迁移途径;在金相显微镜下观察到加铼电极的再结晶晶粒更细小,铼起到了细化再结晶晶粒的作用。在不同工作电流下测得加铼电极的阴极压降更低,铼的加入提升了电极材料的电子发射性能。

As the“heart”of the arcjet,cathode is responsible for heating the gaseous propellant to produce propulsion.Due to the long service cycle and frequent ignition times of satellite,high requirements are put forward for the service life and erosion resistance of cathode materials.In order to seek cathode materials with excellent erosion resistance,based on W-La-Ce-Y and W-La-Y-Zr electrodes,W-La-Ce-Y-Re and W-La-Y-Zr-Re electrode materials were prepared by hydrogen reduction-median frequency sintering.By simulating the actual working condition of the arcjet,the arcing test was carried out at 250 A current,the erosion resistance of each electrode material was studied,and the morphology of the electrode tip after arcing was observed.The results show that the rhenium electrode has less burning loss quality,better tip morphology stability,and better burning loss resistance after 2 h of arc burning.Under SEM,it is observed that the rhenium inhibits the growth of dendrites and weakens the recrystallization degree of tungsten matrix grains.And the migration pathway of rare earth oxides was also discussed.Under the metallographic microscope,it is observed that the recrystallized grains at the tip of the rhenium electrode are finer,and rhenium plays a role in refining the recrystallized grains.The cathode voltage drop of rhenium electrode is lower at different currents.The addition of rhenium improves the electron emission performance of electrode materials.