Stability of nano oxide particles after laser melting : Lab Results

Advanced oxide dispersion-strengthened (ODS) steels are promising candidate materials for application in the core components of fusion reactors and advanced fission reactors as a result of their excellent creep and irradiation resistances. Their superior properties are mostly originated from the presence of the high density of the Y-Ti-O nanoclusters (NCs) with a mean diameter less than 10 nm. Generally, ODS steels are produced using powder metallurgy processes, such as hot extrusion or hot isostatic pressing (HIP). The current manufacturing process of this kind of materials leads to high costs, low fracture toughness, and inflexible part design. An additive manufacturing (AM) process refers to a process by which digital 3D design data is used to build up a component in layers by depositing material. Using this new technique for fabrication of ODS steel component will dramatically increases the shape factors and fracture toughness, and reduce overall processing cost. However, ODS steels are very sensitive to “melted-state” because oxide particles can coarsen quickly in the melt and slag off due to their light weight. Therefore, adoption of AM basis on laser or electron beam melting process is quite challenging task.

Recently, we demonstrated that relatively fine distribution of Y2Ti2O7 oxide particles with mean particle size of 50~100 nm could be retained after quick spot laser melting with enforced cooling system. In present work, feasibility of laser melting process in fabricating advanced ODS steels was first studied. Stability and dispersoid morphology of Y-Ti-O type NCs were examined by TEM and formation mechanisms was discussed.