Electrochemical production of molybdenum refractory metal powders

Akpınar, Bengisu
Molybdenum (Mo) is a refractory metal and mostly used as an alloying agent in cast iron, steels and superalloys to enhance hardenability, strength, toughness and corrosion resistance. It also finds other uses either in the form of a pure metal or an element in, for example, lubricants and catalysts. Traditional metal production methods are not suitable for molybdenum because pure molybdenum has a very high melting point and tends to be oxidized at low temperatures. Hydrogen reduction of molybdenum oxide is a very common way for molybdenum production, but it has two stages during the process. In this study, an alternative method to produce molybdenum metal powder by electrochemical processes is studied. The experiments during this study are divided into two groups, which are using calcium molybdate, (CaMoO4) and using molybdenum disulfide (MoS2) as starting materials. CaMoO4 powder used in the form of pressed pellets was reduced in molten CaCl2-NaCl mixture and it was found that most of CaMoO4 dissolved in CaCl2-NaCl mixture. The experiments yielded 1.9% solubility by weight. MoS2 powder pressed to form pellets were also used as starting material for electrochemical formation of pure molybdenum in molten CaCl2-NaCl salt mixture. Complete reduction of MoS2 to molybdenum refractory metal powder was succeeded under argon gas flow at 750oC. A constant voltage of vi 2,8V was applied between graphite anode and cathode holding either CaMoO4 or MoS2 in all experiments.