Molybdenum is used as an alloying addition in steels, and molybdenum and its alloys are used for electrical and electronic parts, missile and aircraft parts, high-temperature furnace parts, die casting cores, hot-working tools, boring bars, thermocouples, nuclear energy applications, corrosion-resistant equipment, equipment for glass-melting furnaces and metallizing. Molybdenum also finds use as a catalyst in chemical reactions. Molybdenum is not suitable for continued service at temperatures above 500 o C in an oxidizing atmosphere unless protected by an adequate coating.
The mechanical properties of molybdenum and molybdenum alloys greatly depend on the amount of working performed below the recrystallization temperature and on the ductile-to-brittle transition temperature. The minimum recrystallization temperature for molybdenum is 900 o C (1650 o F).
Molybdenum strip has particularly good resistance to corrosion by mineral acids, provided oxidizing agents are not present. It is also resistant to many liquid metals and to most molten glasses. In inert atmospheres, it is unaffected up to 1760 o C by refractory oxides. Molybdenum is relatively inert in hydrogen, ammonia, and nitrogen up to about 1100 o C, but a superficial nitride case may be formed in ammonia or nitrogen.
Consolidation: In most instances, molybdenum is consolidated from powder by compacting under pressure followed by sintering in the range from 1650 to 1900 o C. Some molybdenum is consolidated by a vacuum arc casting method in which a preformed electrode is melted by arc formation in a water-cooled mold.
Hot-working Temperature: Generally forged between 1180 and 1290 o C down to 930 o C
Annealing Temperature: Normal stress-related temperature is 870 to 980 o C.
Recrystallization Temperature: Depends on prior working and condition; 1180 o C for full recrystallization in one hour of a 16mm (5/8 in.) bar reduced 97% by rolling. Suitable Forming Methods: Conventional methods.
Precautions in Forming: Must be heated to the proper temperature relative to its thickness and forming speed. Heat Treatment: Not hardenable by heat treatment but only by work hardening.
Suitable Joining Methods: Can be brazed or joined mechanically, as well as welded by arc, resistance, percussion, flash, and electron beam methods. Arc cast molybdenum is preferred to a powder metallurgy product for welding. Absolute cleanliness of surface is essential. Fusion welding must be carried out in closely controlled inert atmosphere.