On the Effect of Building Direction on the Microstructure and Grain Morphology of a Selective Laser Melted Maraging Stainless Steel

In this study, cylindrical rods of a low carbon Fe-Cr-Ni-Al maraging stainless steel (CX) were fabricated through selective laser melting (SLM) technique for both horizontal direction and cube samples with the dimensions of 15 x 15 x 15 mm. The microstructure and grain morphology of the as-built sample were studied using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). It was observed that in both cases the microstructure of the as-built sample consists of columnar dendrites aligned in the building direction because of the fast-directional cooling presents in the SLM process. However, the microstructural studies revealed that by changing the building method from cube to horizontal, both dendritic and grain structures have a tendency to change. Furthermore, the TEM results showed that different volume fractions of austenite and martensite phases were detected in both directions resulting from complex heat history and wide temperature range during the SLM process.