Microstructure and isothermal oxidation behavior of Nb-Ti-Si-based alloy additively manufactured by powder-feeding laser directed energy deposition

A powder-feeding laser directed energy deposition process has been used for preparing Nb-Ti-Si-based alloys from elemental powder mixtures. The effects of hot isostatic pressing (HIP) on the microstructure evolution and isothermal oxidation at 800 °C and 1250 °C are studied. The as-deposited alloy shows a eutectic microstructure with β-Nb5Si3 dendrites existing in the solid-solution niobium (Nbss) matrix and β-Nb5Si3+Nbss anomalous eutectic in the interdendritic zones. A eutectoid reaction of β-Nb5Si3→Nbss+α-Nb5Si3 occurs after HIP. The oxidation rate for the HIP-processed alloy was 1.33 times that of the as-deposited alloy at 1250 °C. No pest-oxidation is observed on the as-deposited alloy at 800 °C.