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

摘要

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 degrees C and 1250 degrees C are studied. The as-deposited alloy shows a eutectic microstructure with beta-Nb5Si3 dendrites existing in the solid-solution niobium (Nbss) matrix and beta-Nb5Si3+Nbss anomalous eutectic in the interdendritic zones. A eutectoid reaction of beta-Nb5Si3 - Nbss+alpha-Nb5Si3 occurs after HIP. The oxidation rate for the HIP-processed alloy was 1.33 times that of the as-deposited alloy at 1250 degrees C. No pest-oxidation is observed on the as-deposited alloy at 800 degrees C.