Molybdenum, often referred to as "moly", is used in the industry as a heating element for vacuum furnaces or high temperature gaseous atmospheres. It is recommended to use it for parts made of titanium or titanium alloy, instead of graphite heating elements that pollute the room by deposition of graphite elements during the heat treatment operation. Molybdenum, however, is fragile in industry due to rapid changes in temperature and pressure that cause grain magnification and make the piece brittle. In addition, it seems that in practice, 25% more energy is needed to obtain the same temperature in the oven when using molybdenum. It is also more expensive to buy and replace. The graphite element cannot be used in case of too high temperature combined with a too low pressure in order to avoid exceeding the vaporization voltage, in the risk of recovering all the agglomerated graphite in the cold zone of the furnace.
In addition, a small amount of molybdenum hardens the steel. More than two-thirds of molybdenum production is used in alloys. The use of molybdenum alloys soared during the First World War, when demand for tungsten made it rare and high-strength alloys were in high demand. Molybdenum is still used today in high strength alloys and high temperature steels. Special alloys containing molybdenum, such as Hastelloy, are resistant and do not corrode at high temperatures. Moreover, another small amount of molybdenum (1%) hardens the uranium metal. It has been used to make the fuel of the first gas graphite nuclear reactors EDF in 1960.
Molybdenum is used in some parts of aircraft and missiles as well, and also as a filament. Molybdenum is used as a catalyst, particularly in the oil industry, to remove organic sulfur compounds from petroleum. Mixed molybdenum oxide catalysts are used for selective oxidation reactions. Typical applications are the oxidation of propane, propylene or acrylic acrolein. It is also used in the composition of stainless steel used in the marine environment for its high resistance to chemical corrosion.