Characterization of Heat-Affected Powder Generated during Selective Laser Melting of 304L Stainless Steel Powder

The selective laser melting (SLM) process is an Additive Manufacturing (AM) technique that uses a laser to fuse successive layers of powder into near fully dense components. Due to the large energy input from the laser during processing, vaporization and instabilities in the melt pool occur causing the formation of condensate and laser spatter, collectively known as heat-affected powder. Since heat-affected powder settles into the powder bed, the properties of the unconsolidated powder may be altered compromising its reusability. In this study, characterization of 304L heat-affected powder was performed through particle size distribution measurements, x-ray diffraction, metallography, energy-dispersive spectroscopy mapping, and visualization of grain structure with the aid of a focused-ion beam. The results show morphological, microstructural, and surface chemistry differences between the starting powder and heat-affected powder formed during processing which aid in the understanding of laser spatter and condensate that form in the SLM process.