Super duplex 2507 processing by DED AM: response to chemical composition fluctuations submitted to different cooling rates

The broad compositional ranges defined as duplex stainless steels allow each supplier to market the same alloy with a unique chemical profile. This study investigates the hypothesis that these compositional shifts significantly affect the alloy’s final characteristics. Gas atomized powders from two suppliers, both classified as super duplex stainless steel 2507 (SDSS 2507) based on their nominal chemical composition and with similar granulometry, were processed using two solidification kinetics, imposed by directed energy deposition (DED) techniques: Laser and Plasma. An atomized powder presents low $${\text{C}\text{r}}_{\text{e}\text{q}}/{\text{N}\text{i}}_{\text{e}\text{q}}$$ ratio, promoting a ferritic–austenitic solidification mode, which made it difficult to achieve phase balance, despite different cooling rates and post processing heat treatment (PPHT) conditions. The other atomized powder has a high $${\text{C}\text{r}}_{\text{e}\text{q}}/{\text{N}\text{i}}_{\text{e}\text{q}}$$ ratio, which favored a fully ferritic solidification mode, resulting in a phase balance in the as-built condition for laser and plasma DED processes. While the low $${\text{C}\text{r}}_{\text{e}\text{q}}/{\text{N}\text{i}}_{\text{e}\text{q}}$$ ratio alloy had a microstructure composed of a mix of lathy and skeletal ferrite and austenite, high $${\text{C}\text{r}}_{\text{e}\text{q}}/{\text{N}\text{i}}_{\text{e}\text{q}}$$ ratio material exhibited ferritic matrix with intergranular, Widmanstatten and intragranular austenite.