Microstructural Evolution and Micro-Corrosion Behaviour of Flash-Welded U71Mn Joints as a Function of Post-Weld Heat Treatment

The microstructural evolution and corrosion behaviour of railroad flash-butt-welded U71Mn joints and the effect of heat treatment were investigated via scanning electron microscopy and electrochemical measurements. The joint structures were found to mainly comprise pearlite and a few ferrites. The grains became finer and more homogeneous after heat treatment. Additionally, there was a decrease in the corrosion current density (1.71 × 10(−5) A cm(−2)) and increases in the absolute corrosion potential (0.86 mV) and corrosion resistance (1088.83 Ω(−1)cm(2)). This was primarily attributed to the fewer Cl(−) ions at the homogeneous grain boundaries and fewer oxidation reactions on the joints after heat treatment. The findings of this study explain corrosion failure and will guide the development of corrosion-resistant joints for improved railroad quality.