SLM built SS304L was annealed and water quenched to minimize residual stress and avoid carbide precipitation. Mini-tensile characterization of strength and elongation at temperature conditions up to 800°C, along with observations of the associated microstructural transformations were utilized to understand the changes produced in SLM SS304L. As-built and annealed specimens were found to exhibit decreasing strength and elongation with increasing temperature as expected. Carbide precipitates appeared after short times at high temperatures within both as-built and annealed specimens for all cases, but no brittle intermetallic phase development was observed for any of the temperatures investigated. While the lack of Sigma, Chi or Laves phases were anticipated, the premature formation of carbides is unexpected behavior for this composition of SS 304L. It is an indication of higher sensitivity of SLM made material. An additional change in the etch response was also observed between as-built and annealed specimens. It is theorized that annealing caused all ferritic and other residual phases present in as-built SLM SS 304L to fully transform into austenite. The cellular structure observed in the as-built specimen was also dissolved due to annealing and water quenching possibly leading to the strength loss observed.
G. R. Hecht et al., "Elevated Temperature Mechanical and Microstructural Characterization of SLM SS304L," Proceedings of the 30th Annual International Solid Freeform Fabrication Symposium (2019, Austin, TX), pp. 364-375, University of Texas at Austin, Aug 2019.
30th Annual International Solid Freeform Fabrication Symposium -- An Additive Manufacturing Conference, SFF 2019 (2019: Aug. 12-14, Austin, TX)
Materials Science and Engineering
Mechanical and Aerospace Engineering
Article - Conference proceedings
14 Aug 2019