Abstract
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°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°C, the pitting potential of the 3Mo steel decreased remarkably, while that of the W substituted steel hardly changed. During aging, the intermetallic σ and secondary austenite (γ2) phases were precipitated, and the pitting corrosion and intergranular corrosion resistance were significantly decreased after aging at 700–750°C for 10 h, which could be caused by the γ2 formation. The γ2 phase could effect the depletion of molybdenum and chromium in the γ2 /α and γ2/σ boundaries.
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