Abstract
In wire-based directed energy deposition (DED), super duplex stainless steel (SDSS) typically encounters issues including coarse grains, a contradictory relationship between strength and ductility, and inferior wear resistance properties. Herein, we report the introduction of micron-sized NbN particles into DEDed SDSS to achieve an optimized combination of fine microstructure, high strength, impressively larger ductility and better wear resistance. During the DED process, NbN inoculant dissolves and re-precipitates, forming fine NbN and σ particles around 100 nm in size. These NbN particles act as nucleation sites for equiaxed grains, refining both ferrite and austenite. In addition, Nb and N elements left from NbN dissolution enhance the solution strengthening effect. These factors collectively boost hardness and strength in DEDed SDSS. Furthermore, the high Nb level in DEDed SDSS facilitates a dense Cr2O3 layer formation on the specimen surface during wear tests, enhancing wear resistance. Increased Nb and N also lower stacking fault energy (SFE) of SDSS austenite, promoting the occurrence of deformation twinning, and the improvement of work hardening and ductility during plastic deformation. This work shows the great potential of wire-arc DED technology to fabricate SDSS with unique microstructures, excellent wear resistance, and an exceptional combination of strength and ductility for practical applications.
Published Version
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