Effect of vanadium addition on the corrosion behavior of S30432 austenitic heat-resistant steel aged at 650 °C for different times

The effect of 0.18 wt% V addition on the corrosion behavior of S30432 austenitic heat-resistant steel aged at 650 °C for up to 30 h was investigated. In addition to immersion corrosion test, electrochemical methods such as potentiodynamic polarization test, potentiostatic polarization test and double-loop electrochemical potentiodynamic reactivation test were used to compare the corrosion resistance of V-free steel and V-bearing steel. Meanwhile, the corrosion morphology was observed by SEM. The precipitates of V-free steel and V-bearing steel were analyzed by Thermo-Calc software, SEM and TEM. The results show that V addition is beneficial to decrease the immersion corrosion rate and improve the pitting corrosion resistance and intergranular corrosion resistance. The corrosion resistance of V-free steel and V-bearing steel deteriorates with the aging time. The addition of V not only increases the number of secondary MX and Z-phase, but also decreases the number of primary MX and M23C6. The decrease in the number of primary MX reduces the number of corrosion pits. The increase in the number of secondary MX and Z-phase consumes more C, N and Cr, which suppresses the formation of M23C6 and decreases the Cr content in M23C6. It also helps to decrease the number of corrosion pits. Therefore, both the pitting corrosion resistance and the intergranular corrosion resistance of V-bearing steel are improved.