Effects of Cu on the precipitation of intermetallic compounds and the intergranular corrosion of hyper duplex stainless steels

► Cu addition to the base alloy reduces the total amount of intermetallic phases. ► Retardation of intermetallic phases formation due to the decrease of activity of Mo. ► The Cu added alloy reduces the degree of sensitization. To elucidate the effects of Cu on the precipitation of intermetallic compounds and the intergranular corrosion of the hyper duplex stainless steels, a double loop potentiokinetic reactivation test, a scanning electron microscope analysis and thermodynamic calculation were conducted. The addition of Cu to the base alloy reduces the total amount of intermetallic compounds. Particularly, Cu addition to the base alloy results in pronouncedly suppressing the amount of sigma phase whereas it slightly increases chi phases. The Cu added alloy reduces the degree of sensitization due to the delayed precipitation of intermetallic compounds, compared with that of the base alloy.