Effect of aging treatments and microstructural evolution on corrosion resistance of tungsten substituted 2205 duplex stainless steel

摘要

The effect of partial substitution of tungsten for molybdenum on the microstructure and corrosion resistance in 22Cr- 5Ni - 3Mo duplex stainless steel (DSS) has been investigated following aging heat treatments in a temperature range of 600- 1000 deg C. Electrochemical tests were carried out for the evaluation of corrosion resistance. Aging treatment had hardly influenced the general corrosion resistance. With the increase of aging time, the pitting corrosion resistance of the DSSs had decreased. After aging for 2 min at 700 - 900 deg C, the pitting potential of the 3Mo steel decreased remarkably, while that of the W substituted steel hardly changed. During aging, the intermetallic sigma and secondary austenite (gamma_2) phases were precipitated, and the pitting corrosion and intergranular corrosion resistance were significantly decreased after aging at 700 - 750 deg C for 10 h, which could be caused by the gamma_2 formation. The gamma_2 phase could effect the depletion of molybdenum and chromium in the gamma_/alpha and gamma_2/sigma boundaries.