Enhanced pitting resistance of directed energy deposition 316L stainless steel by post-manufacturing heat treatment

The effect of the post-manufacturing heat treatment (PMHT) on the pitting resistance of the directed energy deposition (DED) 316L stainless steel was evaluated. In an as-manufactured DED 316L, a fully austenitic microstructure with typical cellular structure and large columnar grains was observed. The cellular structure was retained after the PMHT of 850 °C/2 h but fully removed by the PMHT of 1150 °C/1 h, while large columnar grains survived in both cases. Both PHMTs significantly improved the pitting resistance of the DED 316L. Especially, the pitting potential of the DED 316L after the PMHT of 1150 °C/1 h was comparable to that of 2205 duplex stainless steel. The excellent pitting resistance of DED 316L after the PMHT of 1150 °C/1 h was caused by the reduction of residual stress, elimination of cellular structure, and presence of large columnar grains.