Surface Remelting-Mediated Improvement in Oxidation Resistance of Cr₂Nb-Containing Nb-Si-Based Alloys at High Temperatures

The poor oxidation resistance of Nb-Si-based alloys generally limits their high-temperature application. A surface remelting strategy for the formation of protective oxide scales and the improvement of oxidation resistance is reported. Electron beam surface melting (EBSM) is performed on arc-melted Nb-14Si-18Ti-12Cr-7Al-0.2Y (at.%) alloys. The microstructure is significantly refined, without altering the phase regime that consists of an Nb solid solution, βNb₅Si₃ and Cr₂Nb. After oxidation at 1200 °C, the EBSM-remelted layer forms a flatter and more compact oxide scale without significant cracking or spalling than that on the arc-melted alloy. A continuous SiO₂ oxide layer is formed within the oxide scale on the EBSM-remelted layer. A reduction of ≈47% in the oxide scale thickness, indicative of improved oxidation resistance, is achieved by the EBSM treatment. The present work provides a promising engineering approach toward the design and fabrication of Nb-Si-based alloys with balanced properties.