Takayuki Watanabe and Munemitsu Usui
Research Laboratory for Nuclear Reactors, Tokyo Institute of Technology, Tokyo 152-8550
Wire arc spraying is one of the most economical thermal plasma coating processes. The disadvantage of wire arc spraying is larger porosity and larger oxide content of the coatings. The purpose of this study is to reduce the oxidation of droplets, and to investigate the effect of atomizing gas on the droplet formation. Lower oxidation at the electrodes results in the stability of the arcing process, and in a decrease in production of AlO in gas phase. The stable arcing process resulting from the lower oxidation leads to the improvement of the coatings. Argon used as the atomizing gas leads to the smallest diameter of the droplets. This is due to the highest temperature of the atomizing gas. Oxidation during the droplet flight is stronger than that at the droplet formation from the electrodes. Argon or nitrogen used as the atomizing gas cannot decrease the oxide content of the droplets.
(Received July 15, 1998; In Final Form September 2, 1998)
arc spraying, aluminum, electrode, coating, droplet, oxidation
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