Additive manufacture of zirconium alloys for thermal propulsion by selective powder deposition

The complex fuel configurations required for nuclear thermal propulsion fuel systems make additive manufacturing a fabrication technology of choice for architectures with flow channels that facilitate effective heat exchange and pressure thresholds. In the present work, additive manufacturing of zirconium-niobium and zirconium vanadium matrices that typically encapsulate low-enriched fuel particles was performed by the selective powder deposition method. Zirconium-niobium (80Zr20Nb) and zirconium-vanadium (56Zr-44V) alloys in contact with graphite, instead of the conventional silica support material, were sintered to consolidate the printed powder forms. Microstructural analyses showed the formation of a zirconium-rich crust at the printed edges in contact with graphite. Thermal conductivity studies were conducted on a laser flash analyser up to 500 °C and both alloys showed comparable thermal conductivity. Mechanical tests in the form of Vickers microhardness indentations and three point bending were performed on zirconium-niobium and zirconium-vanadium alloys. In both studies, the zirconium vanadium showed larger variances in the samples due to the grains of the powder particles sintering in a discretised form and presenting a quasi-composite microstructure. Vickers’ hardness was 527 and 550 HV1/10 for the Zr-V and Zr-Nb, respectively. Sudden failure in the elastic regime showed brittle behaviour in Zr-V, while gradual transition into an inelastic regime in Zr-Nb showed ductile behaviour. Selective powder deposition is a promising additive manufacturing process for the realisation of articles made from zirconium alloys of vanadium and niobium.