Surface Morphology during Tungsten Electrode Operation
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- Category: Tungsten's News
- Published on Wednesday, 06 July 2016 18:49
After 5 seconds arcing, observed tungsten electrode surface morphology found, the tip of electrode has many projections. And this is mainly because the tip affected by current and high-frequency the surface rudimental oxygen will react with tungsten to generate volatile tungsten oxide under heat effect and since arcing was carried out in an argon atmosphere, so the tungsten oxide which produced at the tip will take away by argon gas, leaving relatively clean tungsten grain. However, with arcing time increase, the tungsten which in the middle part of the tip tungsten will react with residual oxygen to produce tungsten oxide. And this tungsten oxide will bring to the top of tip which has higher temperature by argon flow. During the process, tungsten oxide decomposition occurs to form metal tungsten. Besides, tungsten deposition led to form the projection on the tip. However, this structure is prone to produce high frequency discharge and plasma. Not only tungsten and oxygen can react to produce gaseous tungsten oxide, but low-melting substance such as rare earth nitrate in tungsten electrode during arcing process will have diffusion, migration, volatilization and deposition, which is conducive to high-frequency arc starting and stable arcing.
After one minute arcing, observed morphology found due to longer arcing electrode material has undergone obvious recrystallization. The tungsten film which deposited at the before affected by heat will along the grain to growth and only new deposited tungsten film shows amorphous membranous tissue. In the one minute arcing, the tungsten electrode surface covered with typically equiaxed recrystallized structure tungsten film.
After 5 minutes arcing, the root of tip, due to the lower temperature so there is showing processing state fibrous tissue. In addition, compared the electrode tip morphology after five minutes arcing and one minute arcing found there is little change in appearance, indicating that arcing after one minute the electrode enters a relatively stable state and can stable work .
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