A Comparison of Metal Additive and Micro-metal Additive Manufactured 316L Stainless Steel Produced via Selective Laser Melting, Binder Jetting, and Digital Light Processing

Abstract Microfabrication in the form of micro-additive manufacturing (micro-AM) processes has been steadily growing in popularity over the previous two decades to fulfill the demand for components at the micrometer scale. Existing micro-AM technologies have shown the capability to produce components but with limited material selection. Currently, the majority of micro-AM technologies exist for polymeric and ceramic materials, with only a select few metal alloys available across most technologies. One of the more challenging aspects of producing small-scale components is the miniaturization and fabrication of feedstock material. More specifically, for powder-based metal feedstock, this results in a possible change to processing conditions. To better understand the potential changes associated with miniaturization, a comparative study was conducted between additive-manufactured (AM) and micro-AM 316L stainless steel components to examine their resulting microstructures and mechanical performance. Three additive processes were investigated, varied between powder bed fusion (PBF) and sinter-based additive manufacturing (SBAM) technologies. Components were produced via selective laser melting, binder jetting, and digital light processing. Microstructural characterization was performed using light optical and scanning electron microscopy techniques as well as X-ray diffraction. There was no qualitative difference in chemistry or microstructure between the AM and micro-AM processes for both PBF and SBAM components. Electron backscatter diffraction recorded a lack of texture for all components, which was expected for sintered components but uncommon for components produced by PBF. The differences in uniaxial tensile properties and microhardness were mainly attributed to the differences in bulk density, surface roughness, and grain size (or substructure cell size). Bulk densities were recorded as ≥ 96 pct and ≥ ~ 98 pct for the SBAM and PBF components, respectively. The average recorded surface roughness was ~ 1 to 3 µm R a and ~ 3 to 5 µm R a for the SBAM and PBF components, respectively. An almost identical mechanical response was recorded for the SBAM components with low tensile strength (~ 530 to 580 MPa) and high elongation at fracture (~ 50 to 76 pct), whereas a noticeable difference in tensile strength (~ 560 to 750 MPa) and elongation (~ 5 to 40 pct) was recorded between the AM and micro-AM components for PBF.