Microstructural Characterization and Properties of Laser-DED Built Oxide Dispersion Strengthened SS 316 L

Abstract

This paper demonstrates the successful fabrication of a novel Ion-based oxide dispersion strengthened (ODS) stainless steel 316 L (SS 316 L) with directed energy deposition (DED) additive manufacturing. The statistical and spatial hardness, modulus, and grain growth of the as-built ODS-SS 316 L were investigated by accelerated property mapping (XPM) and electron backscattered diffraction (EBSD), respectively. Experimental results showed that the crystal structure of the DED-built ODS-SS 316 L is single phase austenite FCC, with varying microstructure across the interface. On the ODS-SS 316 L side, fine grains are observed whereas the pure SS 316L region contained relatively larger sized and more equiaxed grains. In the interface, elongated grains are discerned with their grain size is lower than the pure SS316L grains. Columnar dendrites are identified near the interface with the growth orientation horizontal to the direction of the laser deposition. The hardness and modulus distribution at room temperature track the microstructural features–overall no drastic changes were observed across the interface. The DED-built ODS SS-316 L has overall higher hardness and modulus than DED-built pure SS 316L. Based on the above findings, the microstructure evolution and reinforcing mechanisms of material strength are discussed.