Enhanced Thermal Stability Of The Cellular Structure Through Nano-Scale Oxide Precipitation In 3d Printed 316l Stainless Steel

The cellular structure is one of the reasons for the improvement of 316 L performance which fabricated by additive manufacturing technology. However, the cellular structure tends to disappear at high temperatures. In this study, oxide nanoparticles were introduced into the 316 L matrix to improve the thermal stability of the cellular structure, this material was successfully fabricated by mechanical alloying followed with laser-powder-bed-fusion (LPBF). The thermal stability of the cellular structure in 316 L was tested with isothermal heat treatment at 1073 K, 1173 K and 1273 K, respectively. The microstructural stability of the cellular was characterized with scanning electron microscopy, transmission electron microscopy (TEM), electron backscatter diffraction, X-ray diffraction measurements and Vickers microhardness testing. The cellular structure was stable at 1073 K due to the dispersed precipitates pining the dislocations at its boundary. The chemical composition of the oxide precipitates with sizes in the range of 10-200 nm was examined by TEM combined with an energy dispersive spectrometry. This work provided a method to enhance the thermal stability of the microstructure of the additively manufactured stainless steel 316 L.