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以WCo75钎料为研究基础,结合分析Co-Nb和Nb-W二元相图,设计了理论成分比例为Co∶W∶Nb=65∶25∶10(%,质量分数)的合金钎料,以期获得温度段合适,符合阴极钎焊标准的高温钎料。对WCo75和Co-W-Nb这两个体系钎料的熔化温度、润湿性以及其铺展后的焊缝形貌成分进行了测试、分析、对比,研究并讨论了Nb的影响。结果表明:加入金属Nb可以有效地将WCo75钎料的熔点由1480.0降至1238.5℃,润湿角也由小于20°减小至5°左右,效果显著。两种钎料都有良好的焊接效果,焊后没有裂纹或熔蚀、熔析等不良缺陷。能够在得到的焊接组织中发现富集相(富Co相靠近自由端而富W相靠近基材),钎料与母材之间有一定的相互扩散。加入Nb后,一方面不会改变钎料层的富集趋势,另一方面能够显著地促进W向Mo母材的扩散,同时,不会因为造成阴极的污染或是毒化而影响其发射效率。
Based on the WCo75 brazing filler metal and the binary phase diagram of Co-Nb and Nb-W, the alloy solder with the theoretical composition ratio of Co:W:Nb = 65:25:10 (mass fraction) was designed, In order to obtain the right temperature section, in line with the standard brazing cathode brazing temperature. The melting temperature and wettability of the WCo75 and Co-W-Nb brazing materials and the morphology of the welded joints after the spreading were tested, analyzed, compared, studied and discussed the influence of Nb. The results show that the addition of Nb can effectively reduce the melting point of WCo75 solder alloy from 1480.0 to 1238.5 ℃ and the wetting angle from less than 20 ° to about 5 °. Both types of brazing filler metal have a good welding effect, no cracks or corrosion after welding, melting and other defects. It is possible to find a rich phase (Co-rich near the free end and a W-rich phase near the substrate) in the resulting welded structure, with a certain interdiffusion between the filler metal and the base metal. The addition of Nb, on the one hand, does not change the tendency of the solder layer to be enriched, on the other hand, it can significantly promote the diffusion of W to the Mo base material without affecting the emission efficiency due to pollution or poisoning of the cathode.