In-situ interstitial alloying during laser powder bed fusion of AISI 316 for superior corrosion resistance

Abstract

The present work explores for the first time additive manufacturing of powder mixtures consisting of Chromium Nitride (Cr2N) and AISI 316L with laser powder bed fusion (L-PBF). The addition of 2.5 wt% Cr2N to an AISI 316L powder resulted in the successful dissolution of both chromium and nitrogen into a fully austenitic stainless steel microstructure. The nitrogen content was augmented from 0.09 wt% in the as-delivered AISI 316L powder to 0.31 wt% in the L-PBF built part, causing a slight expansion of the austenite lattice. Elongated austenite grains with an internal cellular substructure were obtained in both the Cr2N modified 316L and the 316L specimens manufactured by L-PBF. The addition of nitrogen (and chromium) from Cr2N resulted in a Vickers hardness increase of about 40 HV0.1, mainly by interstitial solid solution strengthening. The modification of 316L by the addition of Cr2N significantly improved the corrosion resistance. The improved hardness and corrosion resistance while retaining the manufacturability and cellular microstructure illustrate the potential for modifying the composition and properties of L-PBF 316L with targeted dosing with Cr2N powders.

Keywords

• Austenitic stainless steel
• 316L
• Chromium nitride
• L-PBF
• Corrosion resistance
• Additive manufacturing