Argonne Scientists Investigate 3D-Printed Steels
Steel produced using additive manufacturing falls short compared to steel made by conventional methods. These conclusions were reached by scientists after conducting a series of studies. In particular, 3D printing technologies offer a way to more efficiently produce complex stainless-steel components with greater design flexibility. However, additive manufacturing processes can leave defects in the microscopic structures of steel parts, affecting their performance characteristics.
The research was focused on 316H steel, a commonly used type of stainless steel for nuclear reactor structural components, and Alloy 709 (A709), a new alloy developed for use in advanced reactors.
Both studies revealed important differences between printed steels and their forged or conventionally manufactured equivalent components. They also showed how printed steels respond to heat treatment, which is typically applied to forged materials.
In one study, scientists focused on 316H, a well-known structural material in wrought form, and compared the microstructures of forged and 3D-printed 316H samples using the capabilities of the Argonne Center for Nanoscale Materials. The samples were subjected to heat treatment called solution annealing. The experiments showed that recovery and recrystallization were inhibited by nano-oxides, but at the same time, the nano-oxides increased tensile strength.
Researchers collected detailed structural data and correlated it with mechanical properties, including tensile strength and creep resistance. The laboratory notes that nano-oxides act as a barrier to dislocation movement and the growth of new grains, which causes some striking differences between the response of printed and forged steels to heat treatment. For example, printed samples began recrystallizing at temperatures several hundred degrees higher than their forged counterparts.
The Argonne National Laboratory states that the research results will be used to develop specialized heat treatment methods for steels produced by additive manufacturing, and will also provide fundamental knowledge about 3D-printed steels, which will guide the development of next-generation nuclear reactor components.