Improved Strength-Ductility Synergy and Corrosion Resistance in a Model 45 Steel by Surface Cr Microalloying and Laser Remelting

Abstract

This work uses chromium (Cr) microalloying in a model 45 steel to optimize the strength-ductility synergy. This goal is realized by a microstructural design strategy of introducing heterogeneous structures with nanoprecipitation and solutes at the surface via Cr coating and laser remelting. As a result, increased strength (i.e. ~110MPa in yield strength) and comparable ductility are achieved in the studied 45 steel, compared with the Cr-free substrate. In addition, the self-current corrosion current is also reduced by an order of magnitude. The Cr-rich coatings retained after laser remelting provide certain improvements in corrosion resistance because Cr-rich has a multifaceted effect. A series of microstructural characterizations, including transmission electron microscopy (TEM), scanning electron microscopy (SEM), and electron back-scattered diffraction (EBSD), were utilized to reveal that Cr-rich precipitates and Cr solutes play key roles in the improving of strength-ductility synergy, as quantified by the strengthening model.

Keywords: Steel, Microalloying, Laser melting, Corrosion resistance, mechanical property