High temperature high strength austenitic steel fabricated by laser powder-bed fusion. (1st June 2022)

• Record Type: Journal Article
• Authors: Dryepondt, Sebastien; Nandwana, Peeyush; Unocic, Kinga A.; Kannan, Rangasayee; Fernandez Zelaia, Patxi; List, Fred A.
• Is Part Of: Acta materialia. Volume 231(2022)
• Publication Date: 2022-06-01
• Subjects: Laser powder bed fusion (LPBF) -- Austenitic steel -- Nano carbides -- HK30Nb -- Tensile -- Cellular structure; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2022.117876
• Languages: English
• ISSNs: 1359-6454

Abstract

Graphical abstract: Abstract: Extremely fast cooling rates during laser powder-bed fusion (LPBF) can result in materials with unique microstructures. For LPBF 316L stainless steel, the formation of sub-grain cellular structures with high dislocation density has been linked to superior tensile properties at room temperature. This cellular structure offers also a new route for the development of high temperature LPBF steels with the nucleation of nano-size strengthening carbides in the cell walls. HK30Nb steel (Fe-25Cr-20Ni-Nb-C) was, therefore, fabricated by LPBF to evaluate its potential for high temperature applications. Optimization of the fabrication parameters yielded material with density greater than 99.7%, with nano Nb-rich precipitates in the cell walls. Annealing at 800 °C for 5h resulted in the nucleation and growth of additional precipitates mainly in the cell walls and at grain boundaries. The high dislocation density led to yield strength at 20–900 °C two to three times higher than yield strength for cast HK30Nb and the nano carbides in the cell walls significantly improved the cellular structure stability at 800 °C.