Nanoscale core–shell (Cr,V,Nb)CN precipitation in micro-alloyed steel

This study presents the first direct experimental evidence of core–shell structured (Cr,V,Nb)CN precipitates—featuring a V-rich core and Cr-rich shell—in a micro-alloyed steel. Through advanced characterization techniques including high resolution transmission electron microscopy, energy dispersive X-ray spectroscopy, electron energy loss spectroscopy, and atom probe tomography, it was revealed that this complex carbonitride architecture emerges during simulated industrial coiling and exhibits the potential to resist coarsening, as suggested by the negligible hardness reduction observed during long coiling times. The Cr-rich shell reduces interfacial energy and suppresses solute diffusion, effectively stabilizing the precipitate size. These findings underscore the potential of (Cr,V,Nb)CN core–shell precipitates as a novel strengthening mechanism, providing a cost-effective alternative to Mo- and Ti-based systems and advancing the design of high-performance steels.