Effect of Deformation and Heat Treatment on Intergranular Corrosion Resistance of Domestic Alloy 690

Effect of deformation and heat treatment on intergranular corrosion resistance of domestec alloy 690 has been investigated with testing methods of electrochemical potentiodynamic reactivation (EPR) and ASTM G28-A.The specimens were deformed to 3%～10%,followed by solution treatment at 1080 ℃、 1100 ℃ and 1120 ℃ for 10 or 15 minutes,and then by thermal treatment at 715 ℃ for 10 hours.EPR curves were obtained in a solution of 0.5 mol/L H2SO4 + 0.01 mol/L KSCN at room temperature (25 ℃) with a Potentiostat/Galvanostat PAR 263A.The grain boundary morphology of alloy 690 was investigated after etching in a solution of 2% Br + 98% CH3OH.The results show that aging heat treatment can change the intergranular carbide morphology obviously,which can improve the corrosion resistance of alloy 690.The specimens with 3% deformation and solution treated at 1120 ℃ for 10 minutes,5% deformation and solution treated at 1100 ℃ for 10 minutes,5% deformation and solution treated at 1120 ℃ for 15 minutes exhibited relatively high intergranular corrosion resistance.