Benchmarking of 316L Stainless Steel Manufactured by a Hybrid Additive/Subtractive Technology

Abstract

This research study investigated the hybrid processing of 316L stainless steel using laser powder bed (LPB) processing with high-speed machining in the same build envelope. Benchmarking at four laser powers (160 W, 240 W, 320 W, and 380 W) was undertaken by building additively with machining passes integrated sequentially after every ten deposited layers, followed by the final finishing of select surfaces. The final geometry was inspected against the computer-aided design (CAD) model and showed deviations smaller than 280 µm for the as-built and machined surfaces, which demonstrate the good efficacy of hybrid processing for the net-shape manufacturing of stainless steel products. The arithmetic average roughness values for the printed surfaces, Ra (linear) and Sa (surface), were 11.4 um and 14.9 um, respectively. On the other hand, the vertical and horizontal machined surfaces had considerably lower roughness, with Ra and Sa values ranging between 0.33 µm and 0.70 µm. The 160 W coupon contained layered, interconnected lack of fusion defects which affected the density (7.84 g·cm−3), yield strength (494 MPa), ultimate tensile strength (604 MPa), Young’s modulus (175 GPa), and elongation at break (17.3%). By contrast, at higher laser powers, near-full density was obtained for the 240 W (7.96 g·cm−3), 320 W (7.94 g·cm−3), and 380 W (7.92 g·cm−3) conditions. This, combined with the isolated nature of the small pores, led to the tensile properties surpassing the requirements stipulated in ASTM F3184—16 for 316L stainless steel.

Influence of Hatch Strategy on Crystallographic Texture Evolution, Mechanical Anisotropy of Laser Beam Powder Bed Fused S316L Steel

“…The averaged tensile properties of the samples are summarized in Table 1 . In general, all three sample types’ mechanical properties resemble those published by EOS GmbH [ 41 ] and are consistent with further benchmark values, as summarized by Sarafan et al [ 42 ] Shear failure in textured (high Mn) TWIP steels was reported by Li et al [ 37 ] A Goss texture in those specimens was induced by a rolling process and resulted in a comparable stress–strain curve as well as shear fracture, similar to the present case.…”

Investigation of Microstructures and Tensile Properties of 316L Stainless Steel Fabricated via Laser Powder Bed Fusion

“…In a previous study by Sarafan et al [31], it was demonstrated that the porosity of samples could be influenced by the laser power. Increasing the laser power from 160 W to 380 W resulted in a corresponding increase in density from 98.1% to 99.5%.…”

Preliminary Report on Compositional Specification for Printed 316SS

“…11 However, if the cooling rates are too fast, the -ferrite can be retained even at room temperature and can negatively affect the fracture toughness and corrosion resistance. 18,19 Therefore, a powder composition specification aimed at minimizing the -phase formation at the end of solidification would be critical to avoid the possibility of any retained -ferrite at room temperature. To determine a compositional specification for 316SS-L, 1,000 compositions were chosen, all of which were within the ASTM specifications shown in Table 1.…”