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 - Four alloys were used in this study, two duplex stainless-steel alloys type 2304 and 2205, super duplex stainless steel type 2507 and austenitic stainless-steel alloy type 316L. The alloys were heated to different temperatures, 750, 850, 950 and 1050 oC, for three different times 10 min, 1hr and 4 hrs. Findings - The microstructural investigations showed that 2205 and 2507 were behaved similarly in recovering their microstructures, especially in terms of ferrite:austenite ratio within specific heat treatments and changing the hardness values. The results showed that the microstructure of both alloys was started to change above 750 oC, the largest changes were shown at 850 oC and 950 oC, as the lowest ferrite content was recorded at 850 oC for both alloys. However, the microstructures of both alloys were started to recover at 1050 oC. The reduction in the hardness values was attributed to the formation of residual stress free ferrite grains. 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 carbide precipitation. Research limitations/implications –The microstructural changes which associate with the heat treatments have been recovered for two alloys, further works can be done on welded samples for similar alloys. Originality/value – Finding the exact heat treatments, temperature and time, to recover the microstructural changes of duplex stainless-steel alloys.