Recovery of the microstructural changes of different duplex stainless steel alloys

Purpose To find out the optimum heat treatments to recover the microstructural changes of stainless steel alloys. Design/methodology/approach A total of four alloys were used in this study: two duplex stainless steel (DSS) alloys type 2304 and 2205, super DSS (SDSS) type 2507 and austenitic stainless steel alloy type 316 L. The alloys were heated to different temperatures, 750, 850, 950 and 1,050 degrees C, for three different times, 10 min, 1 and 4 h. Findings The microstructural investigations showed that 2205 and 2507 behaved similarly in recovering their microstructures, especially in terms of the ferrite:austenite ratio within specific heat treatments and changing the hardness values. The results indicated that the microstructure of both alloys started to change above 750 degrees C, the largest changes were shown at 850 and 950 degrees C as the lowest ferrite content (FC%) was recorded at 850 degrees C for both alloys. However, the microstructures of both alloys started to recover at 1,050 degrees C. The reduction in the hardness values was attributed to the formation of new ferrite grains, free of residual stresses. On the other hand, the microstructure of the alloy type 2304 was stable and did not show large changes due to the applied heat treatments, similarly for austenitic alloy except showing chromium (Cr) carbide precipitation. Originality/value Finding the exact heat treatments, temperature and time to recover the microstructural changes of DSS alloys.