Thoriated Tungsten Electrode Microstructure Research after Machining Deformation

To obtain thoriated tungsten electrode should process a series of machining deformation processing on tungsten blank. Machining deformation of thorium tungsten electrode mainly includes swaging cogging, recrystallization annealing, 203 rotary swaging, 202 rotary swaging, 201 rotary swaging, drawing, straightening, polishing, and finally be finished. Selected three typical stages in the whole process analyze thorium tungsten electrode microstructure change, which were sampled in three stages of recrystallization annealing, 202 swaging and finished products.

After recrystallization annealing, tungsten matrix of thoriated tungsten electrode had very obvious grain boundaries, and along the axial direction grain boundaries was relatively flat. Besides, the grains of tungsten matrix were thicker and had certain of extension. There were many fine black spherical particles in electrode internal, which is the second phase.

After 202 rotary swaging, the grains of tungsten matrix became slender, and had clearer boundaries. Different with recrystallization stage, there was a certain fibrotic. The grains of tungsten substrate along the axial direction to extent, the coarse grains became long and thin. What’s more, the second phase distributed more evenly, but still maintained a spherical or near spherical shape.

With deformation increasing, the grain boundary of tungsten matrix in finished thoriated tungsten electrode gradually became blurred, and the crystal grains completely replaced by fibrous tissue. Fibrous tissue elongates along with the axial direction of the electrode. The second phase particles distributed more evenly.

From the above analysis, thorium tungsten electrode during machining deformation, with increasing deformation, the tungsten matrix gradually turns to fibrosis and distribution of second phase particles becomes more uniform. Besides, the second phase is mainly composed of Th, O and W three elements.

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