Effect of Titanium Addition on the Neutral Corrosion Resistance of Welding Overlay

The effect of titanium on the corrosion resistance of slag-free self-shielded flux-cored arc welding overlay was discussed in 3.5wt.%NaCl solution. The results show that the polarization curves of the welding overlays with 3.6 wt.% titanium addition are at the lowest value, and the rest of the polarization curves shows an increasing trend. As the addition of titanium addition further increases to 7.2 wt.%, the highest value is observed. The trend charts of I_corr and E_corr of welding overlays with different Fe-Ti additions are in agreement with polarization curves. In the microstructure of welding overlays, the primary M₇(C, B)₃, M₃(C, B)₃ (M=Cr, Fe mainly), and TiC carbides remain intact, but the matrix is corroded to form concave regions. The corrosion resistance of the welding overlay is the highest at the titanium addition of 7.2 wt.%, which is related to the increase in TiC carbide and higher chromium content in the matrix. However, when the titanium addition is 3.6 wt.%, the appearance of a near-eutectic structure greatly increases the reaction interface of electrochemical corrosion reaction, increases the rate of corrosion reaction, and thus reduces the corrosion resistance.