High temperature high strength austenitic steel fabricated by laser powder-bed fusion
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.
- Publication:
-
Acta Materialia
- Pub Date:
- June 2022
- DOI:
- 10.1016/j.actamat.2022.117876
- Bibcode:
- 2022AcMat.23117876D
- Keywords:
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- Laser powder bed fusion (LPBF);
- Austenitic steel;
- Nano carbides;
- HK30Nb;
- Tensile;
- Cellular structure