Floating regulation and electrochemical corrosion behavior of in-situ synthesized (Nb,Ta)C by electromagnetic field under laser remelting state

Abstract

Based on the aggregation phenomenon of in-situ synthesized micron-scale (Nb,Ta)C, the upward Lorentz force under the electromagnetic field (EMF) was utilized to drive the moving ceramic phase to counteract gravity and achieve surface enhancement. Also, the floating, remelting and dispersion uniformity control of multi-sized (Nb,Ta)C was realized under laser remelting (LR). The regulation mechanism of porosity, surface topography, microstructure and phase evolution by LR under EMF was emphatically revealed. A corresponding relationship between electrochemical corrosion behavior and microstructure was established. Meanwhile, the variation law of hardness between layers was also analyzed systematically. Results revealed that the stirring effect of the EMF-induced Lorentz force under LR enhanced Marangoni convection and reduced temperature gradient, which was beneficial for removing pores and micropores, thereby reducing porosity and improving surface flatness. The incompletely dissolved and tightly aligned large (Nb,Ta)C on the surface greatly increased the hardness and protected the internal microstructure from corrosion in a self-sacrificing manner.