Scientists 3D-print two types of steel in the same layer

The resulting material is stronger than metal alone.
Loukia Papadopoulos
Representational image of a welder.jpg
Representational image of a welder.


Washington State University engineers were inspired by the structural complexity of trees and bones to conceive of a method to 3D‑print two types of steel in the same circular layer, resulting in a bimetallic material that is 33 percent to 42 percent stronger than metal alone.

This is according to a press release by the institution published on Thursday.

Best of all, the new method employs  common inexpensive tools making it convenient for manufacturers and repair shops to use it in the near term. Amit Bandyopadhyay, senior author of the study, noted that the development could potentially be used to make high-performance medical implants or even parts for space travel.

“It has very broad applications because any place that is doing any kind of welding can now expand their design concepts or find applications where they can combine a very hard material and a soft material almost simultaneously,” said Bandyopadhyay, a professor in WSU’s School of Mechanical and Materials Engineering.

The idea behind the new invention came from nature. Trees and bones get their strength from the way layered rings of different materials interact with each other. Tests on the new resulting material showed greater strength than either stainless steel or mild steel have on their own.

The new method even bypasses an old complication that saw 3D printing with multiple metals requiring stopping and changing metal wires. The new technique eliminates that pause and allows welders to combine two or more metals in the same layer while the metals are still hot.

“This method deposits the metals in a circle instead of just in a line. By doing that, it fundamentally departs from what’s been possible,” said in the statement Lile Squires, a WSU mechanical engineering doctoral student and the study’s first author. “Going in a circle essentially allows one material to bear hug the other material, which can’t happen when printing in a straight line or in sandwiched layers.”

The future holds great promise for the new method with applications possible in medical manufacturing processes that print joint replacements with durable titanium on the outside and an inner material such as magnetic steel with healing properties. Even better, structures used in space could be equipped with a high-temperature resistant material surrounding inner material with cooling properties to help it maintain a consistent temperature.

“This concept has both welders printing, so we can use multiple materials in the same layer itself, creating advantages as they combine,” said Bandyopadhyay. “And it doesn’t have to stop at just two materials. It can be expanded.” 

The study is published in the journal Nature Communications.

Study abstract:

Bimetallic wire arc additive manufacturing (AM) has traditionally been limited to depositions characterized by single planar interfaces. This study demonstrates a more complex radial interface concept, with in situ mechanical interlocking and as-built properties suggesting a prestressed compressive effect. A 308 L stainless core is surrounded by a mild steel casing, incrementally maintaining the interface throughout the Z-direction. A small difference in the thermal expansion coefficient between these steels creates residual stresses at their interface. X-ray diffraction analysis confirms phase purity and microstructural characterization reveals columnar grain growth independent of layer transitions. Hardness values are consistent with thermal dissipation characteristics, and the compressive strength of the bimetallic structures shows a 33% to 42% improvement over monolithic controls. Our results demonstrate that biomimetic radial bimetallic variation is feasible with improved mechanical response over monolithic compositions, providing a basis for advanced structural design and implementation using arc-based metal AM.

Add Interesting Engineering to your Google News feed.
Add Interesting Engineering to your Google News feed.
message circleSHOW COMMENT (1)chevron
Job Board