| The effect of partial replacement of Mo with W on the corrosion resistance of simulated heat-affected zone (HAZ) in 22Cr-5Ni base duplex stainless steels has been investigated. The steels were simulated with various times at the cooling stage in the temperature range of 1200∼800℃(Δt_(1200/800)). In order to evaluate the intergranular and pitting corrosion resistance, Heuy test and electrochemical pitting corrosion test were carried out. Cooling rate and the substitution of W for Mo affected on the microstructure of duplex stainless steels. The amount of austenite phase in the heat affected zone increased linearly with decrease of cooling rate. The grain size in the HAZ also increased approximately linearly with decrease of cooling rate. Corrosion weight loss was varied with the cooling rate at the range of Δt_(1200/800) = 5∼270 sec, which could be influenced by the increase of the amount of autente phase, element partitioning in δ and γ-phases and the increase of γ-grain size at the cooling stage. At Δt _(1200/800) = 33∼270 sec, W-substituted alloy showed better corrosion resistance than the alloy containing only Mo. The W-substituted duplex stainless steel showed the enhanced corrosion resistance only when Δt_(1200/800) $gt; 33 sec. If Δt_(1200/800) is less than 14 sec, the steel only with Mo showed better corrosion resistance of HAZ. |
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