Microstructural Investigations on Super Duplex Stainless Steel UNS S32750 Fabricated by Blown-Powder Directed Laser Deposition

This work deals with the microstructural features and texture characterizations of a super duplex stainless steel (SDSS) grade UNS S32750 fabricated by directed laser deposition (DLD). Local zones depleted in austenite underneath the fusion line of each DLD pass were detected. Extensive nucleation of submicron squarish intragranular (IG)-austenite following the near Kurdjumov-Sachs (K-S) orientation relationship with their ferritic matrix was revealed by Transmission Electron Microscopy (TEM). A considerable increase in precipitation of IG-austenite enhanced the average content of the austenite from the bottom to the top along the building height. Electron backscattered diffraction (EBSD) observations showed that a strong and single solidification texture of Cube (C);{100}〈001〉 accommodated in ferrite was partly transformed into the weak texture of austenite with three components, including Goss (G);{110}〈001〉, Rotated-G;{110}〈011〉, and Rotated-C;{100}〈011〉, formed in two layers on the body of the block with the building heights of 45 and 60 mm. The material has shown to be more susceptible to the texture in layers with higher build heights due to the dominant population of IG-austenite.