A team of researchers at the Indian Institute of Science (IISc), led by Koushik Viswanathan, Assistant Professor at the Department of Mechanical Engineering, have reportedly identified an alternative technique to produce metal powders for Additive Manufacturing by using an abrasion-based process.
Metal powders used for Additive Manufacturing are predominantly produced using atomisation, a process in which a molten metal stream is broken up into fine droplets using gas or water jets. However, despite its widespread use, explains the IISc researchers, atomisation returns poor yield, is relatively expensive and limited in the types of materials. The alternative technique developed by the researchers is said to side-step these problems.
In the metal grinding industry, the material removed, known as swarf, is often discarded as a waste product. It is commonly stringy in shape, like metal chips, but can also include perfectly spherical particles. Scientists have long theorised that these particles go through a melting process, which results in the spherical shape. But this raises some interesting questions, such as whether the heat from the grinding causes the melting, or if there is actually any melting at all?
Viswanathan’s team has shown that these powder metal particles do indeed form as a result of melting due to high heat from oxidation, in an exothermic reaction at the surface layer. The team refined this process to produce large quantities of spherical powders, which are further processed to be used as stock material in Additive Manufacturing. The study is said to illustrate that these powder particles perform just as well as commercial gas atomised powders, when used in metal Additive Manufacturing.
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 powders, and the quality of the final powders appear to be very competitive when compared with conventional gas atomised powders.”
Regarding the applications of their findings, Viswanathan added, “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.”
Harish Singh Dhami, a PhD student at the Department of Mechanical Engineering and co-author of this study, noted, “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 reported that making metal powder using abrasion also has potential in other high-performance applications such as in aircraft engines, where a high degree of specification is required.
The full paper titled ‘Production of powders for metal Additive Manufacturing applications using surface grinding’, by Harish Singh Dhami, Priti Ranjan Panda, and Koushik Viswanathan, was published in Manufacturing Letters, Volume 32, 2022, ISSN 2213-8463