Effects of Solution-Annealing Temperature on the Precipitation of Secondary Phases and the Associated Pitting Corrosion Resistance in Hyper Duplex Stainless Steel

The effects of the solution-annealing temperature on the precipitation of secondary phases and the associated pitting corrosion resistance in hyper duplex stainless steel after aging at 1123K were investigated in a highly concentrated chloride solution. Increasing the solution annealing temperature from 1333 to 1413 K retarded the formation of the secondary phases owing to a decrease in both the number of preferential precipitation sites such as the ferrite/austenite interface and the activities of Cr, Mo and W. The slow rate of degradation of the pitting corrosion resistance of the alloy with the increase in the solution annealing temperature appears to be caused by the retardation of the precipitation of the sigma phase. Based on the results of the precipitation of secondary phases and electrochemical tests, the optimal solution annealing temperature was determined to be 1373 K.