Rare Earth Doped Tungsten Electrode Morphology Effect by Rare Earth Doping Quantity

Rare earth doping quantity not only affects rare earth doped tungsten electrode’s welding ability and burning resistance, but also has some impact on electrodes morphology. Using powder metallurgy method to produced tungsten electrodes doped with three rare earth oxides, and according to different rare doping content the electrodes are divided into A electrode and B electrode. The A electrode rare earth ratio is La₂O₃: CeO₂: Y₂O₃ = 1: 2: 1, and the B electrode rare earth ratio is the ratio of the electrode B is La₂O₃: CeO₂: Y₂O₃ = 1: 1: 3. Analysis two kinds of rare earth doped tungsten electrodes and ceriated tungsten electrode’s morphology to further understand the impact of rare earth doping amount on rare earth doped tungsten electrode morphology.

Analyzing three kinds of electrode processing states section topography photos found the rare earth oxides in three kinds of electrodes has different shape and distribution. Ceriated tungsten electrode formed a very fine and uniform fibrous CeO₂ phase. The A electrode rare earth phase is also fibrous, but uneven, appeared a small amount of fiber breakage. The B electrodes rare earth phase are particles, and the particle and particle link by particle clusters, indicating they are formed by big particles breakage during processing.

After burning test, electrode surface morphology has taken place great changes. Ceriated tungsten electrode tip appeared annular projection, through EDX found them to be cerium oxide, indicating in a large number of cerium oxide enriched to the electrode surface during welding. The A electrode tip has plenty of bulk composite rare earth oxide, and it is composed of smaller particles. The B electrode has special tip morphology. There are many smooth pyramids on matrix surface, which is located in the center of the grain, and a small amount of pyramids has fracture on the top to form some voids. Therefore, the surface of the B electrode is also some small voids, indicating the surface of the B electrode was melted in the welding.

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