Microstructure and oxidation resistance of laser remelted Nb-18Ti-14Si-9Al alloy

Nb–Si alloy has the potential for application in aviation engine component due to its excellent high-temperature performance. In this work, laser remelting treatment was carried out for Nb-18Ti-14Si-9Al. The microstructure of remelted alloy was composed of fine Nbss+T2 eutectic cells, this was significantly different from coarse Nbss+T2 of as-cast alloy. After 850 °C/3 h oxidation, 10.46 μm oxide scale with cracks and holes was formed for the substrate alloy. 8 μm oxidation scale with a few pores was formed for remelted alloy, moreover the microstructure of the scale perpetuated fine eutectic characteristic of the remelted alloy. After 18 h oxidation, the compact oxide scale of the remelted alloy was about 17 μm thick, and oxidation still only occurred in the remelted Nbss+T2 zone. The refine eutectic structure of remelted alloy promoted uniform O diffusion in Nbss and would not cause cracks in the surrounding T2 silicide. Laser remelting was proved to an effective strategy to improve the oxidation resistance of Nb–Si alloys.