纳米级和微米级稀土氧化物掺杂W-La2O3-Y2O3-ZrO2 阴极尖端的组织和性能

Microstructure and Properties of Nanometer- and Micrometer-Sized Rare-Earth Oxide Doped W-La2O3-Y2O3-ZrO2 Cathode Tip

摘要:

使用粉末冶金法将纳米级（70–80 nm）和微米级（500–600 nm）稀土氧化物（La₂O₃，Y₂O₃）与钨粉混合，随后通过冷等静压、中频感应烧结、旋锻、拉拔等一系列工艺制备了W-1.5La₂O₃-0.1Y₂O₃-0.1ZrO₂（质量分数，%）材料。对含有纳米和微米尺寸稀土氧化物的阴极样品使用相同的焊接电流，分别进行了0.5、1、2 h的氩弧焊。结果表明，具有纳米级稀土氧化物的样品在焊接过程中表现出更高的工作稳定性，烧损同比降低了近85.4%。此外，随着工作时间的延长，阴极尖端不同区域的稀土氧化物聚集度显著增加。结合COMSOL Multiphysics温度模拟发现，第二相的扩散活化能降低了近34%。这是因为更为细小的第二相有效地控制了钨基体组织的演变，保留了大量晶界作为通道，促进了活性物质在电子发射过程中的扩散。

Abstract:

Nanometer-(70?80 nm) and micrometer-sized (500?600 nm) rare-earth (RE) oxides (La₂O₃, Y₂0₃) were separately mixed with tungsten powder by a mechanical alloying method. Afterwards, the W-1.5La₂O₃-0.1Y₂O₃-0.1ZrO₂ (wt%) was prepared by cold isostatic pressing, medium-frequency induction sintering, rotary forging, and drawing. Then we performed tungsten argon arc welding (TIG) under the same welding current for 0.5, 1, and 2 h on the cathode samples containing, separately, nanometer- and micrometer-sized RE oxides. Results show that the sample with nanometer-sized RE oxides exhibits higher working stability during the welding process, and the burning loss is decreased by nearly 85.4%. Moreover, with prolonging the working time, the aggregation degree of RE oxides in different regions of the tip significantly increases. Combined with the temperature simulation by COMSOL Multiphysics, we found that the diffusion activation energy of the second phase is decreased by nearly 34%. This is because the finer second phase effectively controls the evolution of the tungsten matrix structure, thus preserving many grain boundaries as channels and promoting the diffusion of active substances.