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Refractory Metals

Refractory Metals

Date posted: October 6, 2017 // Refractory Metals

The adjective “refractory” is used to describe a class of metals that display some special qualities. The two most important qualities are an exceptionally high melting point and an equally exceptional degree of durability that serves to make them especially resistant to corrosion and to physical wear and tear. In addition, they are chemically inert, non-magnetic, and of relatively high density. Definitions regarding precisely which elements should be considered as belonging to this group differ, but all agree that it should contain molybdenum, niobium, rhenium, tantalum and tungsten, all of which have melting points greater than 2200 °C. A wider definition based upon the lower figure of 1850 °C, adds nine additional elements – chromium, hafnium, iridium, osmium, rhodium, ruthenium, titanium, and vanadium.

Used individually, or alloyed in a variety of combinations, the role of refractory metals in materials science has led to numerous important applications within a wide range of industries. The most commonly used of these is molybdenum. Its strength and resistance to wear at high temperatures, coupled with its low frictional coefficient, has led to its widespread inclusion in lubricating oils and grease for use in vehicle engines and axles.

Topping the table with a melting point of 3410 °C, tungsten has gained a host of industrial applications, one of the earliest being the manufacture of the filaments used in the rapidly disappearing incandescent domestic light globes and the electrodes in super-bright arc lighting. Today, its exceptional toughness and thermal characteristics have earned tungsten a role in everything from anti-tank shells and rocket nozzles to arc welding, high-temperature furnace components, and toughened drill bits. One relatively new field in which refractory metals have proved to be invaluable is the semiconductor industry. Here, molybdenum and tungsten are commonly used as contact materials in components like heat sinks, thyristors, transistors, and silicon diodes.

Often these specialised metallic elements are used to modify the properties of other substances, using techniques such as physical vapour deposition (PVD) to produce thin films or coatings and sputtering to create actual bonding with the treated items. The resulting enhancements to the treated items serve to make them more resistant to corrosion and physical wear, like the elements used to treat them.

Based in Midrand, LIT Africa is recognised as a South African leader in the field of materials science. Our main focus is on specialised glass and processing technology, and includes the supply of high-quality refractory metals and components for use in a wide variety of applications, such as PVD coating, tungsten inert gas welding, and the manufacture of high-pressure discharge lamps, dipped beam shields, and electronic components.