Synthesis of β-WC /SUB 1-x/ in an atmospheric-pressure, thermal plasma jet reactor

Studies of the chemical reactions between α-WC and CH4 as well as between WO3 and CH4 in an atmospheric argon plasma jet reactor reveal that the high-temperature tungsten carbide (β-WB /SUB 1-x/ ) may be formed by injecting either α-WC or WO3 with methane as carrier gas into an argon plasma jet. The maximum conversion of α-WC into β-WC /SUB 1-x/ reaches 52%, whereas conversion ratios in excess of 98% are observed when WO3 is used as the primary reactant. X-ray diffraction studies indicate a new FCC phase with a lattice parameter smaller than that of β-WC /SUB 1-x/ which is typically produced in some of the reactions. This new phase shows a sharp lattice parameter change between 700 and 8000C upon annealing in argon. The temperature of transition of β-WC /SUB 1-x/ to the other two more common carbide phases occurs around 4700C. The β-WC /SUB 1-x/ is more stable than β-W2C to acid attack and its resistance is approximately the same as that of α-WC