Influence of Solution Treatment Temperature on Microstructural Properties of an Industrially Forged UNS S32750/1.4410/F53 Super Duplex Stainless Steel (SDSS) Alloy

Abstract

Abstract:In this present study, the influence of solution annealing temperature on microstructural properties of a forged Super Duplex Stainless Steel (SDSS) was investigated by SEM-BSE (Scanning Electron Microscopy-Backscattered Electrons) and SEM-EBSD (Scanning Electron Microscopy-Electron Backscatter Diffraction) techniques. A brief solution treatment was applied to the forged super duplex alloy, at different temperatures between 800 • C and 1100 • C, with a constant holding time of 0.6 ks (10 min). Microstructural characteristics such as nature, weight fraction, distribution and morphology of constituent phases, average grain-size and grain misorientation were analysed in relation to the solution annealing temperature. Experimental results have shown that the constituent phases in the SDSS alloy are δ-Fe, γ-Fe and σ (Cr-Fe) and that their properties are influenced by the solution treatment temperature. SEM examinations revealed microstructural modifications induced by the Cr rich precipitates along the δ/γ and δ/δ grain boundaries, which may significantly affect the toughness and the corrosion resistance of the alloy. Solution annealing at 1100 • C led to complete dissolution of σ (Cr-Fe) phase, the microstructure being formed of primary δ-Fe and γ-Fe. The orientation relationship between δ/δ, γ/γ and δ/γ grains was determined by electron back scattering diffraction (EBSD). Both primary constituent phase's microhardness and global microhardness were determined.

Evaluation of Optimal Forging Temperature Range for an Industrial UNS S32750 SDSS Alloy Using SEM-EBSD Analysis

“…Additionally, it can be seen that the δ-Fe phase is enriched in Cr, Mo, W, and Si (Cr and Mo are ferrite stabilizing elements) and lean in Fe, Ni, Mn, and Cu, when compared to the γ-Fe phase (Ni and Cu are austenite stabilizing elements) and vice versa. These observations were consistent with previous works by the authors [19,26,27]. 5 show a series of representative SEM-EBSD composite images (×200 and ×1000, respectively) resulting from the microstructural investigation of UNS S32750 super-duplex stainless steel in the structural state obtained after forging at 800 • C, which shows that the microstructure of the alloy is relatively homogeneous, but consists of grains fragmented by the deformation process.…”

Influence of Aging Treatment on Microstructure and Tensile Properties of a Hot Deformed UNS S32750 Super Duplex Stainless Steel (SDSS) Alloy

“…In the case of duplex stainless steels, during isothermal heating, at temperatures below 600 • C, few phase transformation mechanisms can occur [16][17][18][19], with the most important one being spinodal decomposition of the δ-phase into coherent α-phase (Fe-enriched) and α'-phase (Cr-enriched), leading to the following important changes in alloy's exhibited mechanical properties: a high decrease of toughness, an increase in hardness, a small decrease in elongation to fracture, and little or no changes in ultimate tensile strength and yield strength [38]. Other important transformation mechanisms that can occur are represented by the precipitation of secondary phases, such as the R-phase, G-phase, and chromium nitrides [12][13][14][15].…”

“…Considering the TM processing specific features, the samples´reference frame, indicated in Figure 2a, assumes the following main directions: RD-rolling direction, TD-transverse direction, and ND-normal direction. The sample's microstructure was analysed in the plane defined The metallographic preparation procedure applied to all the samples collected from all TM processed states is presented and detailed elsewhere [19][20][21]. The microstructure was investigated by SEM techniques, with the purpose of observing the microstructural constituent phases and the changes occurred during TM processing.…”

“…All data were rounded to the nearest whole number, in MPa and J (for strength and impact properties), while the elongation was rounded to 0.5% (i.e., according to EN 10002-1). The metallographic preparation procedure applied to all the samples collected from all TM processed states is presented and detailed elsewhere [19][20][21]. The microstructure was investigated by SEM techniques, with the purpose of observing the microstructural constituent phases and the changes occurred during TM processing.…”

Research on Energy-Saving Scheduling of a Forging Stock Charging Furnace Based on an Improved SPEA2 Algorithm

“…Currently, studies about heating furnace energy conservation are mainly focused on equipment optimization and reform [1], waste gas heat recycling and utilization [2], development and application of new materials (non-quenched and tempered steel, alloy metals, and so on) [3][4][5], improvement of heat treatment process [6,7], etc. However, the studies about energy-saving scheduling are still limited.…”