Laser Directed Energy Deposition Additive Manufacturing of Oxide Dispersion Strengthened (ODS) FeCrAl Under a Reactive Atmosphere

Oxide dispersion strengthened (ODS) FeCrAl alloys combine the improved high-temperature corrosion resistance provided by Al additions with the improved mechanical properties and irradiation resistance provided by fine nanoscale precipitate dispersions. Directed energy deposition (DED) additive manufacturing (AM) providing oxygen during powder consolidation allows for potential increased geometric complexity, local microstructure control, and part throughput while avoiding the pitfalls often plaguing conventional mechanical alloying (MA) based ODS manufacturing of batch-to-batch variability, long lead times, low throughput, and anisotropic mechanical properties. In this work laser-based DED AM of ODS FeCrAl was capable of significant oxygen retention (up to 0.11 wt%) and moderate precipitate number densities (~10²⁰ m^-3) [approximately 10 to the 20th power per cubic meter) while maintaining acceptable part quality (part density > 99%). Unfortunately, significant amounts of oxide forming elements were wasted by precipitate agglomeration. The influence of Si, Ti, and O additions on oxide wettability, metal-oxide interfacial energy, and oxide incorporation into an Fe matrix was tested in an attempt to mitigate deleterious oxide agglomeration and maximize nanoscale precipitate production.