New 3D-printing method combines two types of steel in the same layer

Engineers at Washington State University have developed a groundbreaking 3D-printing method inspired by the structural complexity of trees and bones. By employing two welding machines, they can 3D-print two different types of steel in the same circular layer. The resulting bimetallic material exhibits a remarkable strength increase of 33% to 42% compared to each metal individually. This strength enhancement is attributed to the pressure generated between the metals as they cool together.

What sets this method apart is its utilization of readily available and cost-effective tools, making it feasible for manufacturers and repair shops to adopt in the near future. With further advancements, it holds potential for manufacturing high-performance medical implants and even components for space exploration. Amit Bandyopadhyay, the senior author of the study published in the journal Nature Communications, highlights the broad applications of this technique, enabling the combination of hard and soft materials simultaneously in various welding processes.

Taking inspiration from nature’s design, particularly the layered rings of different materials found in trees and bones, the WSU research team replicated this concept using metals. They integrated the welding equipment commonly found in automotive and machine shops into a computer numerical control (CNC) machine. This innovative hybrid setup allows for the precise programming of computer-guided manufacturing, with two welding heads working in tandem to create intricate parts.

In a demonstration of the new 3D-printing method, two welding heads work one right after the other on a circular layer to print two metals: an outer casing of cheaper “mild” steel and a corrosion-resistant, stainless-steel core inside. Since the metals shrink at different rates as they cool, internal pressure is created—essentially clamping the metals together. Tests on the result showed greater strength than either stainless steel or mild steel has on their own. Credit: Washington State University

In a demonstration, the engineers successfully utilized two welding heads to sequentially print two metals in a circular layer, capitalizing on their distinct advantages. They created a corrosion-resistant, stainless-steel core surrounded by an outer casing of more economical “mild” steel, commonly used in infrastructure like bridges and railroads. As the metals cool, their differential rates of shrinkage generate internal pressure, effectively clamping the materials together. Rigorous testing confirmed that the resulting bimetallic structure exhibited significantly greater strength than either stainless steel or mild steel alone.

Traditional 3D printing techniques involving multiple metals necessitate stopping and changing metal wires, interrupting the process. However, the newly developed method eliminates this pause and enables the simultaneous deposition of two or more metals within the same layer while they remain hot.

Lile Squires, the study’s first author and a mechanical engineering doctoral student at WSU, explains that the unique circular deposition of metals in this approach departs from the conventional linear or layered printing. By following a circular path, one material essentially embraces the other, creating a synergistic interaction that is unattainable when printing in a straight line or with sandwiched layers.

The ability to enhance the strength of 3D-printed metal parts layer by layer holds great promise for automotive shops, enabling the rapid production of robust and customized steel components. For example, bimetallic axle shafts resistant to torque or cost-effective, high-performance brake rotors could be developed.

Looking ahead, the researchers envision transformative applications in medical manufacturing, such as the production of joint replacements featuring a durable titanium exterior paired with an inner material possessing magnetic properties for enhanced healing. Similarly, space structures could incorporate a high-temperature resistant material surrounding an inner layer with cooling properties to maintain consistent temperatures.

Bandyopadhyay emphasizes that this method empowers welders to simultaneously print with multiple materials within the same layer, presenting numerous advantages. Moreover, the technique can extend beyond two materials, offering opportunities for further expansion and innovation.

Recognizing its significant potential, the researchers and Washington State University have filed a provisional patent application to protect this groundbreaking development.

Source: Washington State University

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