Researchers from the Indian Institute of Science (IISc), one of India’s leading technology and research institutes, have identified and developed an alternative low-cost technique to produce metal 3D printing powders. The team of researchers was led by Koushik Viswanathan, Assistant Professor at the Department of Mechanical Engineering and the new technique provides an alternative to atomisation, the common technique to forming metal powders.
Priti Ranjan Panda, a PhD student at IISc’s Centre for Product Design and Manufacturing and one of the authors of the study, commented, “We have an alternative, more economical and inherently scalable route for making metal 3D printing powders, and the quality of the final powders appear to be very competitive when compared with conventional gas atomised powders.”
A majority of the metal 3D printing technologies use powder materials which are fused together with the help of lasers. An important characteristic of these powders is its morphology. However, despite the widespread use of atomisation processes to create the powders, it results in poor yield, moreover it is expensive, and is inflexible in the types of materials it can handle.
Novel Technology for Metal 3D Printing Powder Production
The team knew of the existing problems in the atomisation process and sought to resolve them. It is well know that in the metal grinding industry, the removed material, known as swarf, is frequently discarded as a waste product. It is typically stringy in shape, like metal chips, but it also frequently produces perfectly spherical particles. Scientists have long hypothesised that these bodies go through a melting process to acquire their spherical shape, which raises some intriguing questions, such as whether the heat from the grinding causes the melting. Is there any melting?
The team demonstrated that these powdery metal bodies form at the surface layer as a result of melting caused by high heat from oxidation, an exothermic reaction. They refined the process to produce large quantities of spherical powders, which are collected and processed further to be used as stock material in additive manufacturing. In the context of metal AM, their research shows that these particles perform just as well as commercial gas atomised powders.
“There has been significant recent interest in adopting metal AM because by nature, it enables significant customisation and allows design freedom. 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.”– Koushik Viswanathan, Assistant Professor at the Department of Mechanical Engineering
Harish Singh Dhami, a PhD student at the Department of Mechanical Engineering and co-author of this study added, “Reducing the cost of the AM process (via economical powders) can widen the range of materials in situations such as manufacturing of biomedical implants, which could become cheaper and more accessible. The researchers say that making metal powder using abrasion also has potential in other high-performance applications such as in aircraft engines, where a high degree of specificity and sophistication are required.”
Currently, metal powders are typically produced at an atomisation facility, requiring transport for casting and recycling, thus setting up a big supply chain. This works for abundant metals like aluminium, Viswanathan points out, but for strategic materials (such as tantalum and lithium), where extraction alone is a complex process, it would be favourable to have a scalable process for producing metal powders. Then, in principle, the entire supply chain can be housed within a single facility – a possibility that their technique could offer.
Reference: Harish Singh Dhami, Priti Ranjan Panda, Koushik Viswanathan, Production of powders for metal additive manufacturing applications using surface grinding, Manufacturing Letters, Volume 32, 2022, ISSN 2213-8463 https://doi.org/10.1016/j.mfglet.2022.02.004
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