Tungsten - its strength and weakness
Updated: Jul 8, 2019
WE love tungsten! At 3410 degrees C, it has the highest melting point of all metals. This makes it an incredibly useful metal, even if the green lobby manage to get rid of all the ordinary light bulbs out there. Electrical contacts, x-ray targets, windings & heating elements, space, missile, tools and any number of high temperature applications.
Tungsten’s very high melting point is also its weakness: It makes it very hard to work: Melting & casting is practically impossible, sawing, machining & forming very difficult.
Luckily tungsten is easily deposited by CVD, normally by the reaction of tungsten hexafluoride with hydrogen. This can be achieved at the modest temperature of 500 degrees C. Many different materials can be coated with a layer of tungsten from a micron to a few millimeters thick.
The relatively low deposition temperature means that steels can be coated (with a suitable interlayer) without distortion or the need for post-coating re-hardening.
By depositing a thick coating onto a removable/ dissolvable/ meltable/ burnable mould, free-standing CVD tungsten shapes can be created. Thin-walled, boats, tubes, crucibles in 100% dense, high purity tungsten can be made. This is practically impossible by any other route.