Effect of Ferrite Proportion and Precipitates on Dual‐Phase Corrosion of S32750 Super Duplex Stainless Steel with Different Annealing Temperatures

Abstract

The effects of ferrite proportion and precipitates on the dual‐phase corrosion properties of S32750 super duplex stainless steel are investigated with different annealing temperatures. When the specimens are annealed at 900 and 950 °C, respectively, the dual‐phase microstructure changes due to the precipitation of σ phase. Meanwhile, the passivation behavior of the specimens weakens, and the pitting corrosion potential decreases. With the increase in annealing temperature, especially over 1150 °C, the ferrite content and the grain size increase significantly and the pitting resistance equivalent of the ferrite phase decreases. The optimal annealing temperature of the tested steel is 1050–1100 °C. Under this condition, the dual‐phase proportion is close to 1:1, no obvious secondary phase precipitates in the matrix, and both the ferrite and the austenite phases present excellent corrosion resistances.

Effect of Isothermal Holding at 750 °C and 900 °C on Microstructure and Properties of Cast Duplex Stainless Steel Containing 24% Cr-5% Ni-2.5% Mo-2.5% Cu

“…34–49%), Cr (12%), and N (2.1%) ( Figure 11 ). This may indicate the presence of the complex non-equilibrium nitrides that have been described in the literature [ 16 ]. Their formation was triggered by both the technological process (the deliberate introduction of Nb) and the supersaturation of ferrite with nitrogen during the cooling of the tested cast steel.…”

“…Recently, articles have been published on the additional strengthening of the surfaces of duplex steel castings, further improving their wear resistance [ 14 , 15 ]. The complex chemical composition of duplex steels (especially of the third and fourth generations—referred to in the literature as Super- and Hyper-DSS [ 16 , 17 ]) promotes the release of undesirable and harmful secondary phases in the microstructures of these materials [ 18 ]. During their operation in corrosive environments, the presence of these phases increases the steel’s susceptibility to intercrystalline, pitting, and stress corrosion while also deteriorating its strength and welding properties [ 19 ].…”

Effect of Heat Treatment Atmospheres on Microstructure Evolution and corrosion resistance of 2205 Duplex Stainless Steel weldments

“…Improper annealing temperature promotes formation of intermetallic precipitation which depends on presence of Cr, Mo. Furthermore, several studies showed the Nearby zone of the Sigma phase depleted of Mo, Cr, whereas sigma phase enriched with Cr, Mo, and presence of intermetallic phases make duplex stainless steel was prone to Embrittlement [4], and consequently low corrosion resistance and deteriorated mechanical properties [9], [10] [11], [12] [13].…”

“…The welding in uence not just be restricted to chemical composition, affect also the volume fraction of ferrite because of heat [18], [19]. Several studies indicate that the appropriate temperature for annealing is between 1000 to 1200 by quenching water [9][8], [20][10].…”

“…Wei Shen [9] indicated that the optimal annealing temperature for DSS without the presence of intermetallic precipitation is between 1050 and1100 . Whereas Zhang[8] clari ed the effects of short time heat treatment after welding at (a small scale from the temperature where choice) 1020, 1050, 1080, 1100 and 1150 and con rmed the optimal annealing temperatures (no intermetallic) are 1050 and 1080 .…”