Induction plasma spheroidization of tungsten and molybdenum powders
JIANG Xian-Liang, M. BOULOS
Trans. Nonferrous Met. SOC.China
abstract:The melting, evaporation and oxidation behaviors as well as the solidificationphenomena of tungsten and molybdenumin induction plasma were studied. Scanning electron microscopy was used to examine the morphology and the cross section of plasma-processedpowders. X-ray diffraction was used to analyze the oxides formed on the particle surface of these two metals. The influence of spray chamber pressure on the spheroidizationand oxidation phenomena was discussed. The results show that fewer Mo particles than W particles are spheroidizedat the same powder feed rate under the same plasma spray condition althoughmolybdenum has a lower melting point. A smallfraction of tungsten is evaporizedand condensedeither on the surfaceof tungstenparticles nearby or on the wall of spray chamber.Tungsten oxides were found in tungsten powderprocessedunder soft vacuum condition.Extremely large grainsform inside some spheroidizedparticlesof tungstenpowder.
keywords:Tungsten; Oxidation; Molybdenum; Spheroidization; Evaporation; Melting; Induction plasma
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