Evaluation of microstructural properties and investigation of corrosion behavior of P460NH welded steel using E8018-G electrode

One of the applications of P460NH micro-alloy steel is its use in pressure vessel tanks. Electrode E8018-G can be used for welding  this steel. In this study, to obtain the optimal welding parameters, the arc process based on ASME IX standard was used. Then, by sampling from the weld section, Vickers hardness test was performed and hardness profiles were drawn in different areas. Then the microstructure of each area was examined and compared with the hardness test results. The corrosion behavior of the heat affected zone, weld zone and base metal was investigated separately using the TOEFL polarization test in a 3.5% solution of NaCl. The results showed that the weld zone had the highest percentage of perlite (62%) and the base metal had the highest percentage of ferrite (‌73%). Also, the heat affected zone has the highest hardness number (298) and the base metal has the lowest value (210) in the Vickers scale. Evaluation of corrosion behavior of different areas also showed that the heat affected zone has the highest corrosion potential (-.651v) and the lowest corrosion current density (1.75×10-5 A/cm2). This is while the base metal has the lowest corrosion potential (-.691v) and the highest corrosion current density (1.2×10-6 A/cm2) compared to the weld metal and the heat affected zone.