Selective laser melting of austenitic oxide dispersion strengthened steel: Processing, microstructural evolution and strengthening mechanisms

Abstract

Oxide dispersion strengthened (ODS) alloys exhibit superior mechanical properties due to the presence of nano-sized thermally stable oxide particles. However, manufacturing of ODS alloys is very complex and composed of numerous time consuming steps such as mechanical alloying, which is one of the main barriers toward the widespread application of ODS alloys. Light mixing of 304L stainless steel powder with sub-micrometer size yttria particles was coupled with selective laser melting (SLM) to produce 304L ODS nanocomposite. The added yttria was dissolved in the matrix due to the high intensity of the laser and altered the rheological properties of the melt and caused balling effect. The SLM 304L ODS alloy presented cellular substructure with a uniform dispersion of yttrium silicate (Y–Si–O) spherical nanoparticles, range 10–80 nm. As a result, the SLM 304L ODS alloy showed a high ultimate tensile strength of ~700 MPa, ductility of ~32% and microhardness of ~350 HV. The underlying mechanism for this strength and ductility improvement are identified. This study provides deep insight into an alternative method of producing ODS alloys with fewer steps and capable of manufacturing complex design geometries.