Analisys of hot deformation behavior of super duplex stainless steel UNS S32760 through processing maps

Abstract

The need for materials with higher strength and corrosion resistance in corrosive environments, such as in the oil extraction in saline media, has led to the use of super duplex stainless steels in projects such as the Pre-sal. The manufacture of these materials involves the step of thermomechanical processing, whose performance depends on the workability of the material. Processing conditions in which the super duplex stainless steel UNS S32760 can be worked safely and in which the material can fail were investigated in this presentation. The physical simulation was performed by means of hot torsion testing.The tests were performed at temperatures ranging from 900°C to 1200°C and strain rates of 0.01s-¹ to 10s-¹. The evolution of strain rate sensitivity of flow stress (m) for deformation of 0.5 at all temperatures investigated here was determined. After attaining the values of m for each deformation condition, the values of the power dissipation efficiency (η) were calculated, an instability criterion (ξ) was applied, and processing maps were constructed. Using these maps, the effects of deformation conditions on the power dissipation efficiency and the material plastic instability were discussed. The domains of processing maps, the observed microstructures and the shape of plastic flow stress curves were associated.

Precipitation condition and effect of volume fraction on corrosion properties of secondary phase on casted super-duplex stainless steel UNS S32750

“…Duplex stainless steel (DSS) is a dual-phase (austenite and ferrite, which are materials having high strength and corrosion resistance) stainless steel (Chen and Yang, 2001; Park et al , 2005; Iacoviello et al , 2005; Chen et al , 2002; Pohl et al , 2007). DSS can be classified into four categories based on the pitting resistance equivalent number (PREN), and the PREN (calculated as Wt.% Cr + 3.3 Wt.% Mo + 16 Wt.% N) for super-duplex stainless steel (SDSS) ranges from 40 to 50 (Chen et al , 2002; Pohl et al , 2007; Dias and Balancin, 2016; Martins and Casteletti, 2009; Pardal et al , 2009). DSS needs solution annealing to optimize the corrosion resistance, but high alloys of DSS make high corrosion resistance difficult because segregation is easy (Angelini et al , 2004; Tan et al , 2009; Wei et al , 2009; Laycock et al , 1998; Davanageri and Kadoli, 2015).…”

Effect of cooling rate after heat treatment on pitting corrosion of super duplex stainless steel UNS S 32750

“…Therefore, recently developed advanced alloys such as super duplex stainless steel (SDSS) have excellent mechanical and electrochemical properties at high pressure and corrosion (Chen and Yang, 2001;Park et al, 2005;Iacoviello et al, 2005;Chen et al, 2002). SDSS contains various alloying elements, with each elemental concentration ranging from 24 to 26 Wt.% chromium (Cr) (Pohl et al, 2007;Dias and Balancin, 2016;Martins and Casteletti, 2009;Pardal et al, 2009;Angelini et al, 2004). SDSS is a dual-phase stainless steel that constitutes austenite (high corrosion-resistant) and ferrite (high strength) (Chen et al, 2002;Pohl et al, 2007;Dias and Balancin, 2016;Martins and Casteletti, 2009;Pardal et al, 2009;Angelini et al, 2004).…”

“…SDSS contains various alloying elements, with each elemental concentration ranging from 24 to 26 Wt.% chromium (Cr) (Pohl et al, 2007;Dias and Balancin, 2016;Martins and Casteletti, 2009;Pardal et al, 2009;Angelini et al, 2004). SDSS is a dual-phase stainless steel that constitutes austenite (high corrosion-resistant) and ferrite (high strength) (Chen et al, 2002;Pohl et al, 2007;Dias and Balancin, 2016;Martins and Casteletti, 2009;Pardal et al, 2009;Angelini et al, 2004). Therefore, SDSS has excellent properties such as corrosion resistance, wear resistance and strength at high pressure and corrosion (Tan et al, 2009;Wei et al, 2009;Laycock et al, 1998).…”

“…Corrosion resistance must be satisfied for the application of SDSS in extreme environments. The following aspects of corrosion resistance of SDSS are to be investigated: effect of microstructure, chemical composition, corrosion resistance as function of heat treatment temperature (Kim et al, 2015;Jang et al, 2003;Dias and Balancin, 2016;Martins and Casteletti, 2009;Pardal et al, 2009;Angelini et al, 2004). Owing to the changed microstructure as a function of heat treatment temperature, previous studies on microstructure of SDSS focused on heat treatment temperature.…”

“…Specifically, only a few studies on corrosion resistance of microstructure using heat treatment have been reported (Kim et al, 2015;Jang et al, 2003;Nilsson and Wilson, 1993;Nilsson, 1992;Chen and Yang, 2001). The microstructure and corrosion resistance of SDSS on exposure to heat were studied (Dias and Balancin, 2016;Martins and Casteletti, 2009;Pardal et al, 2009;Angelini et al, 2004;Tan et al, 2009). No study has assessed the effect of the cooling rate.…”