Abstract
In this paper, the effects of Ti and Cu addition on inclusion modification and corrosion behavior in the simulated coarse-grained heat-affected zone (CGHAZ) of low-alloy steels were investigated by using in-situ scanning vibration electrode technique (SVET), scanning electron microscope/energy-dispersive X-ray spectroscopy (SEM/EDS), and electrochemical workstation. The results demonstrated that the complex inclusions formed in Cu-bearing steel were (Ti, Al, Mn)-Ox-MnS, which was similar to that in base steel. Hence, localized corrosion was initiated by the dissolution of MnS. However, the main inclusions in Ti-bearing steels were modified into TiN-Al2O3/TiN, and the localized corrosion was initiated by the dissolution of high deformation region at inclusion/matrix interface. With increased interface density of inclusions in steels, the corrosion rate increased in the following order: Base steel ≈ Cu-bearing steel < Ti-bearing steel. Owing to the existence of Cu-enriched rust layer, the Cu-bearing steel shows a similar corrosion resistance with base steel.
Highlights
Low-alloy steel has been widely used as a construction material in the marine environment, owing to its remarkable mechanical properties and low cost [1,2,3]
Localized corrosion induced by inclusions is usually in conjunction with a high local corrosion rate, which can result in a structural failure [7]
The impact of Ti and Cu addition on microstructure and toughness in simulated coarse-grained heat-affected zone (CGHAZ) of low-alloy steels [15,16] and the localized corrosion behavior induced by inclusions, such as Al2O3, MnS, were discussed in detail [29,30,31]
Summary
Low-alloy steel has been widely used as a construction material in the marine environment, owing to its remarkable mechanical properties and low cost [1,2,3]. To improve the mechanical property of the coarse-grained heat-affected zone (CGHAZ) induced by high heat input welding, alloying elements, such as Ti and Cu, were added to refine the microstructure during the welding process [11,12,13]. The addition of alloying elements can significantly affect the corrosion resistance of the steel, owing to its influence on protective rust layer formation, inclusion number density, size distribution, and chemical composition [18,19,20]. The impact of Ti and Cu addition on microstructure and toughness in simulated CGHAZ of low-alloy steels [15,16] and the localized corrosion behavior induced by inclusions, such as Al2O3, MnS, were discussed in detail [29,30,31]. The impact of inclusion number density, average diameter, and chemical composition on corrosion behavior was clarified
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