Using Lasers to ‘Heat and Beat’ 3D-Printed Steel to Help Reduce Costs

University of Cambridge, United Kingdom

A new method for metal 3D printing aims to make more efficient use of resources by allowing structural modifications to be “programmed” into metal alloys during 3D printing, fine-tuning their properties without the “heating and beating” process that’s been in use for thousands of years.

The new method combines the best qualities of both worlds: the complex shapes that 3D printing makes possible, and the ability to engineer the structure and properties of metals that traditional methods allow. The results are reported in the journal Nature Communications.

“There’s a lot of promise around 3D printing, but it’s still not in wide use in industry, mostly because of high production costs,” said Research Lead Matteo Seita. “One of the main drivers of these costs is the amount of tweaking that materials need after production.”

“The reason why heating and beating is so effective is because it changes the internal structure of the material, allowing control over its properties,” said Seita. “That’s why it’s still in use after thousands of years.”

One of the major downsides of current 3D-printing techniques is an inability to control the internal structure in the same way, which is why so much post-production alteration is required.

“We’re trying to come up with ways to restore some of that structural engineering capability without the need for heating and beating, which would in turn help reduce costs,” said Seita. “If you can control the properties you want in metals, you can leverage the greener aspects of 3D printing.”

Working with colleagues in Singapore, Switzerland, Finland, and Australia, Seita developed a new “recipe” for 3D-printed metal that allows a high degree of control over the internal structure of the material as it is being melted by a laser.

By controlling the way that the material solidifies after melting, and the amount of heat that is generated during the process, the researchers can program the properties of the end material. Normally, metals are designed to be strong and tough, so that they are safe to use in structural applications. 3D-printed metals are inherently strong but also brittle.

The strategy the researchers developed gives full control over both strength and toughness, by triggering a controlled reconfiguration of the microstructure when the 3D-printed metal part is placed in a furnace at relatively low temperature. Their method uses conventional laser-based 3D-printing technologies, but with a small tweak to the process.

“We found that the laser can be used as a ‘microscopic hammer’ to harden the metal during 3D printing,” said Seita. “However, melting the metal a second time with the same laser relaxes the metal’s structure, allowing the structural reconfiguration to take place when the part is placed in the furnace.”

Their 3D-printed steel, which was designed theoretically and validated experimentally, was made with alternating regions of strong and tough material, making its performance comparable to steel that’s been made through heating and beating.

“We think this method could help reduce the costs of metal 3D printing, which could in turn improve the sustainability of the metal manufacturing industry,” said Seita. “In the near future, we also hope to be able to bypass the low-temperature treatment in the furnace, further reducing the number of steps required before using 3D-printed parts in engineering applications.”

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