Additive Manufacturing to Produce High-Strength Stainless Steel by NIST and Argonne National Laboratory
According to the design news website reported on November 3, researchers at the National Institute of Standards and Technology (NIST), the University of Wisconsin-Madison, and Argonne National Laboratory have created one of the strongest stainless steels in existence, 17-4 precipitation hardening (PH)Stainless Steel has innovated a 3D printing method that prints stainless steel with the same properties as stainless steel made by traditional methods.
This stainless steel is a strong, corrosion-resistant alloy used in the construction of cargo ships, passenger aircraft, and nuclear power plants. This innovation marks the continuous 3D printing of 17-4 PH steel while retaining its original properties.
While the use of 3D printing to make plastic parts has become more common across industries, powder-based metal additive manufacturing (AD) is more complex, in part due to the very rapid temperature changes during printing, the powder experiences rapid fluctuations in a short period of time. Additive manufacturing of metals essentially welds millions of tiny powder-like particles together using high-energy sources such as lasers, melts them into a liquid, and then cools them into a solid.
But because the cooling rate is high, creating an extreme non-equilibrium state, the process of rapid heating and cooling can cause rapid changes in the crystal structure of the atoms in the steel, making it impossible to determine what is happening in the material at the atomic level, so it is impossible to make precise The crystal structure cannot determine the optimum state of the printed material.
To address these issues, the researchers used synchronous x-ray diffraction (XRD) to study the crystal structure during rapid temperature changes, so they could determine the internal structure of the martensite during printing. The researchers used Argonne’s Advanced Photon Source (APS) to shoot high-energy X-rays into the steel sample during the printing process. In this way, the researchers were able to map out how the steel’s crystal structure changed during printing.
Although iron is the main component of 17-4 PH steel, its specific composition includes as many as 12 different chemical elements. With a clearer understanding of the structural changes in steel during the 3D printing process, researchers can fine-tune the composition of this steel and thus control the 3D printing results. This approach can also be applied to other materials, using XRD to optimize other alloys for 3D printing and provide useful information for building and testing computer models that can predict the final quality of printed parts.