TSC SB RAS proposes a quick energy-efficient approach to producing rounded powder alloys for 3D printing

Scientists from Tomsk Scientific Center SB RAS have synthesized spheroidized powders based on Ni-Al intermetallic compounds in a combustion wave. In additive manufacturing techniques such as selective laser melting, preference is given to spherical granules, since they facilitate the fabrication of complex heat-resistant products and coatings used in energy and aerospace industries. The findings have been published in the peer-reviewed journal Alloys and Compounds .

– This is the first time we produced intermetallic spherical powders in a single step process driven by a combustion wave propagating through a specially prepared reactive mixture with minimal external energy input. Compared to conventional techniques, which typically involve multi-stage processing and requires high-temperature furnaces and plasma arc equipment, our method for producing such powders is superior in terms of energy efficiency and simplicity, – explained Alexander Kirdyashkin, leading researcher at the Laboratory of Combustion Technology at TNC SB RAS, Candidate of Physical and Mathematical Sciences.

In additive technologies, when turning hard, low-ductility materials into complex structures of precise shape (gas turbine blade, for instance) that do not require mechanical post-processing, using rounded powders is the go-to option. Micro-sized spherical granules “flow like water” and can be easily fed to where they need to go to ensure uniform layer-by-layer sintering when processed with a laser or an electron beam.

To spheroidize the granules, a special modifying additive that reacts during combustion must be included in the initial mixture. Without this additive, irregularly shaped intermetallic sinters requiring subsequent mechanical processing are formed and the particles turn out to have the wrong shape.

– During combustion, this additive decomposes and releases gases that induce localized agitation of the reacting mixture’s powder particles. This agitation promotes melting and makes the particles coalesce into neat spherical shapes. To make sure it works it is important to set the right reaction temperature. If it’s too hot or too cold, nothing will happen. It takes one millisecond to form a sphere within the combustion wave and they form one by one as the wave propagates through the mixture, – explained the researcher.

To produce rounded powder alloy, the reactive mixture is loaded into a laboratory reactor where combustion is initiated; it proceeds spontaneously at temperatures up to 1600°C. The scientists demonstrated that a wide range of alloy compositions could be synthesized. Using a reactor with about three liters capacity, up to 10 kg of product can be produced in 30 minutes. The market price for one kilogram of similar powder made by other methods starts at over 100$.

The scientists have successfully tested these powders in 3D printing already. The resulting intermetallic materials are characterized by heat resistance and oxidation stability. The research continues and new compositions of spherical intermetallics with various alloy additives are to be developed soon.

© TSC SB RAS Press Center