Corrosion Resistant Feedstock Modification in Additively Manufactured 316L

Abstract

Additive manufacturing (AM) is a disruptive technology that has the potential to dramatically improve the US Department of Defense supply chain. The corrosion performance of these AM materials is not well understood and contradicts equivalent conventionally-manufactured materials. AM316L steel frequently has defects and pores that are 25-µm or less, and these are implicated as the cause for localized corrosion including crevice and pitting. The 316L feedstock used in manufacturing AM316L contains up to 0.03% wt carbon, and the depletion of chromium due to sensitization and formation of Cr26C3 is yet another cited reason for localized corrosion. We demonstrate that mixing the feedstock with small amounts of certain ceramic materials could might improve these shortcomings. The surface of this new material - AM316L-MMC (metal matrix composite) - is hydrophobic, in contrast to the hydrophilicity of AM316L, and shows little or no evidence of pitting and crevice corrosion in aqueous solutions of 5%, 30% and 60% FeCl3. It also remains free of pitting and crevice corrosion under anodic polarization in aqueous 3.5% sodium chloride electrolyte.