Investigation of Heat-Affected 304L SS Powder and Its Effect on Built Parts in Selective Laser Melting

Selective laser melting (SLM) is a powder bed based additive manufacturing process in which a layer of powder is laid over the surface of a substrate and a laser with sufficient energy is employed to selectively melt particles to build a part layer by layer. During the SLM process, dark smoke was observed coming off of the powder bed surface where the laser was interacting with powder. This phenomenon resulted from heat-affected powder that was visibly different than the base powder. Since the concentration of the heat-affected powder differs throughout the build chamber as a result of the recirculating argon gas flow, powder samples from different regions were collected for analysis. The heat-affected powder samples were analyzed by scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), and x-ray diffraction (XRD) in order to distinguish differences between the heat-affected powder and the base 304L stainless steel powder. The influences of the heat-affected powder on the microstructure and tensile properties of parts built in different areas of the build chamber are also investigated.