Molybdenum is a refractory metal with a high melting point and high strength, an indispensable additive in both the steel industry and high-temperature lubrication. Its largest use is in alloy steels: trace additions of molybdenum significantly improve hardenability, high-temperature strength and resistance to temper embrittlement, so structural steels, tool steels, stainless steels and superalloys all contain molybdenum, widely used in oil and gas pipelines, pressure vessels, automotive gears and military armor. In superalloys, molybdenum is used in gas turbines and hot-extrusion dies, retaining hardness even at red heat. In lubrication, molybdenum disulfide (MoS2)'s layered structure makes it an excellent solid-lubricant additive, blended into greases, sprayed dry films and powder-metallurgy solid lubricants for bearings and gears under high-temperature, heavy-load and vacuum conditions. In catalysis, molybdenum-cobalt and molybdenum-nickel catalysts are used in petroleum hydrodesulfurization and heavy-oil upgrading, key auxiliaries of the refining industry. Molybdenum wire and sheet are also used in glass-melting electrodes and vacuum heating elements because of their low vapor pressure at high temperature and non-wetting behavior with glass.
Molybdenum disulfide (MoS2) is a black scaly powder, the main constituent of natural molybdenite; because its layers slide easily over one another, it is an excellent solid lubricant used in high-temperature greases, dry-film coatings and self-lubricating modification of plastics such as nylon. Molybdenum trioxide (MoO3) is the intermediate oxide for producing molybdenum metal and molybdates, and is also a component of dehydrogenation and desulfurization catalysts and a colorant in ceramics and glazes. Molybdates (such as sodium molybdate and ammonium molybdate) are widely used as metal corrosion inhibitors, scale inhibitors in cooling-water systems and trace agricultural fertilizers, and are also precursors for preparing petroleum hydrodesulfurization catalysts. Molybdenite (MoS2) itself is the main ore from which molybdenum is refined, so its identity as lubricant and as metallurgical feedstock coincides in a single mineral.
