Alternative to metal atomization

Researchers at the Indian Institute of Science (IISc) have identified a way to produce metal powders that they say is cheaper and more productive than atomization.

They say that it is also more flexible in the types of materials it can handle.

In the metal grinding industry, the material removed – called swarf – is often discarded as a waste product. It is commonly stringy in shape, like metal chips, but it often also throws up perfectly spherical particles, according to Koushik Viswanathan, assistant professor at the department of mechanical engineering, who led the research. “Scientists have long theorised that these bodies go through a melting process to take up the spherical shape, thus posing some interesting questions – does the heat from the grinding cause the melting? Is there melting at all?” a press release said.

The research reportedly showed that these powdery metal bodies form as a result of melting due to high heat from oxidation, an exothermic reaction, at the surface layer. The scientists then refined this process to produce large quantities of spherical powders, which are collected and processed further to be used as stock material in AM. According to the IISc, the study shows that these particles perform “just as well” as commercial gas atomized powders when used for metal additive manufacturing (AM).

“We have an alternative, more economical and inherently scalable route for making metal powders, and the quality of the final powders appear to be very competitive when compared with conventional gas atomised powders,” said Priti Ranjan Panda, a PhD student who is one of the authors of the study.

“There has been significant recent interest in adopting metal AM because by nature, it enables significant customisation and allows design freedom,” said Dr Viswanathan. However, the large cost of stock metal powders has been the stumbling block. We hope that our work will open new doors to making cheaper and more accessible metal powders.”

Making metal powder using abrasion also has potential in applications such as in aircraft engines, where a high degree of powder specificity and sophistication is required, the researchers said.

Currently, metal powders are typically produced at an atomization facility, requiring transport for casting and recycling, thus setting up a big supply chain. This works for abundant metals like aluminium, according to Dr Viswanathan, but for strategic materials (such as tantalum and lithium), where extraction itself is a complex process, with this new technique process the entire supply chain can be housed within a single facility.