Wei, S., Soh, V., Lau, K. B., Wuu, D., Lee, J. J., Ngo, A., & Wang, P. (2026). In situ nitrogen atmosphere strengthening and cracking control in highly textured FeCrAl alloys fabricated by laser powder bed fusion. Journal of Alloys and Compounds, 188310. https://doi.org/10.1016/j.jallcom.2026.188310
Abstract:
The role of nitrogen atmosphere in the laser powder bed fusion (LPBF) of Fe10Cr4Al alloys was systematically investigated, focusing on the mechanisms of nitrogen-induced strengthening and cracking. A compositional gradient approach was first used to determine the maximum amount of Al addition in Fe10Cr, which was identified as approximately 4 wt.% Al. Pre-alloyed Fe10Cr4Al powders were then fabricated under both argon and nitrogen atmospheres. While crack-free samples were readily obtained under argon, nitrogen led to cold cracking even after extensive parameter optimization. Microstructural characterization combined with thermodynamic calculations showed that nitrogen uptake (~0.04 wt.%) promotes the formation of complex Al2O3–AlN core–shell precipitates, which segregate to (sub)grain boundaries and induce intergranular embrittlement. To mitigate this issue, 80 ppm B was introduced via FeB addition. Cold cracking was not observed in the B-modified alloy fabricated under nitrogen, confirming the grain boundary toughening effect of boron. Tensile testing revealed higher yield and ultimate strengths (~537 MPa and~557 MPa, respectively) compared to argon-printed samples (~459 MPa and ~499 MPa), but ductility is lowered (~2% compared to ~5%) due to nitrogen-induced precipitation. These results provide insights into the coupled effects of atmosphere and composition on LPBF alloys, while demonstrating microalloying as an effective pathway to extend the processability window of FeCrAl alloys under nitrogen atmosphere.
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Funding Info:
This research / project is supported by the A*star - Additive manufacturing of in situ Aluminum-based composites for aerospace applications
Grant Reference no. : M24N8c0106
This research / project is supported by the A*star - Development of High- Performance Electric Traction Module
Grant Reference no. : M22K4a0044
This research / project is supported by the A*star - 4D Additive Manufacturing (4DAM) of Smart Structures- WP3
Grant Reference no. : M24N3b0028