What are the benefits of using refractory metals?
Refractory metals are a classification of metallic elements that possess properties that make them more durable and resilient than other standard metals. While the definition of this term varies slightly, one of the defining characteristics of refractory metals is their extraordinarily high melting point. Generally, the term “refractory metals” is applied to all metals possessing melting points higher than 3630°F (2000°C).
The metals most commonly included in this classification are niobium, tantalum, tungsten, molybdenum and rhenium. Broader definitions also include metals with melting points above 3362°F (1850°C) and include: chromium, zirconium, vanadium, titanium, rhodium, hafnium, ruthenium, osmium and iridium.
In addition to high melting points, refractory metals also offer several additional benefits, such as high corrosion resistance, excellent heat conductivity and electrical conductivity, high hardness at room temperature, low thermal capacity and extreme resistance to deformation. (To learn more about ascertaining the hardness of these and other materials, read 5 Ways to Measure the Hardness of Materials.)
Due to their desirable characteristics, refractory metals are typically alloyed with other metals for numerous aggressive, demanding and high-performance applications. For example, tungsten, which has the highest melting point of all refractory metals, is beneficial in applications where high-temperature resistance is required.
Tungsten wire filaments are used in the majority of household incandescent lighting equipment and industrial arc lamps. This metal is also used in gas tungsten arc welding (GTAW) (also known as tungsten inert gas (TIG) welding) for permanent, non-consumable electrodes. Tungsten and molybdenum also have relatively low thermal capacities and are highly resistant to molten glass and quartz, making them ideal for furnace dies, mandrels, skids and supports.
Another essential benefit of refractory metals is their ability to improve the mechanical and chemical properties of metal alloys. Tantalum, one of the most corrosion resistant refractory metals, can be combined with other metals to vastly improve the corrosion resistance of the resulting alloy. Many instruments in the medical and surgical fields are required to be sanitary, wear resistant and free of contaminants at all times. As such, metal alloys with relatively small amounts of tantalum (and also chromium) are preferred due to their corrosion resistance in acidic environments.
The inertness of tantalum and other refractory metals are also crucial in the medical sector due to their chemical inertness and biocompatibility, i.e., these metals do not produce toxic products or trigger adverse immunological responses when exposed to bodily fluids.
The other beneficial properties of refractory metals (hardness, deformation resistance, electrical conductivity, etc.) can be passed on by combining them with other metals. This allows the resulting alloy to be used in applications or environments where the use of only standard metals is either unfeasible or impractical.