INDUSTRIAL MANUFACTURING
absence of an alternative, only a mixed powder has so far been used to make tungsten usable for components with complex geometries. The main disadvantage of such mixtures, however, results from the different melting points of tungsten (around 3,400°C) and of nickel and iron, both of which change their physical state at around 1,500°C. As a result, a large part of the two added substances evaporates in an uncontrolled manner during the melting process in the further processing process. This is because the boiling points of nickel and iron are already around 2,700°C and 3,000°C respectively. Thanks to the pre- alloying in the process developed by Gobran, on the other hand, all three elements are combined as a multiphase material in each individual powder particle, so that their composition and distribution in the end product can be precisely controlled and no loss of the binder metals has to be accepted. According to the common standardised
variants, the new alloy can be produced with 80 to 98.5% (weight) tungsten, 0.1 to 15%
(weight) nickel and 0.1 to 10% (weight) iron and/or copper. This achieves a density of the end product of 17 to 18.8 g/cm3, which is desirable for applications in the aluminium industry, tool manufacture and for alpha and gamma radiation shielding. “The higher the proportion of tungsten in the end product, the more resistant it is to molten aluminium and the better its thermal conductivity,” explains Gobran. “If, on the other hand, good ductility and mechanical machinability play a greater role, the proportion of tungsten in the alloy can also be reduced accordingly. The composition can therefore always be adapted to the specific application and the respective complexity of the shape.” During the comminution process as part of the manufacturing process, the flow behaviour and the grain size of the powder between 10 and 200µm can also be determined. In this way, the alloy is individually prepared for the desired type of further processing – such as plasma coating processes or additive manufacturing.
Upcycling materials If, for example, the hot-work steel previously used for thin and conical cooling channels in cast aluminium chill-moulds is replaced by the tungsten alloy developed by Gobran, the application benefits not only from the heavy metal’s resistance to corrosion and erosion. Compared to steel, tungsten also has the advantage of much higher thermal conductivity, so that the wear on the chill- moulds can be massively reduced. Due to its higher density, the alloy product is also an alternative to poisonous lead, which is used not only for radiation shielding, but also as a stabiliser – for example in the tool industry. “Another special feature of our alloy is that we can make the powder from scraps or chips,” adds Gdoura. “This is a big step forward from both an economic and environmental perspective, as it allows us to recycle and upcycle waste products from conventional processes.”
Bayerische Metallwerke GmbH www.wolfram-industrie.d
During the comminution process as part of the manufacturing process, the flow behaviour and the grain size of the powder between 10 and 200µm can also be determined. In this way, the alloy is individually prepared for the desired type of further processing.
OCTOBER 2021 | ELECTRONICS TODAY 31
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