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

Abstract

The deformation temperature of Super-Duplex Stainless Steels (SDSS) is a key factor defining the number of phases, their proportions, and their arrangement in space, with the main role for the hot plastic processing on the industrial scale. The main scope of the study was to determine the optimal forging temperature of UNS S32750 Super-Duplex Stainless Steel by means of the SEM-EBSD technique. The alloy was forged at different temperatures between 800 • C and 1300 • C, after which the most representative samples were analysed by SEM-EBSD. Microstructural characteristics as nature, distribution, morphology, and relative proportion of constituent phases, grain form, homogeneity, and dynamic recrystallization of the structure were analysed in relation to forging temperature. Primary phases as δ-Fe and γ-Fe were identified in all structural states of the steel, irrespective of the deformation temperature. Secondary phases σ-(Cr-Fe) and χ-(Fe-Cr-Mo), identified only under 1050 • C, have a strong negative effect on hot formability because they are fragile. The conclusion was that the optimal forging temperature range for the UNS S32750 steel is 1050-1300 • C because between these temperatures the structure is composed only of ferrite and austenite, without other harmful secondary alloy phases. Due to the dynamic recrystallization, the plasticity of the material also increases in this thermal range.

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

“…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.…”

Simultaneously Enhanced Strength, Toughness and Ductility of Cast 40Cr Steels Strengthened by Trace Biphase TiCx-TiB2 Nanoparticles

“…The typical ferrite-pearlite hybrid structure of the medium-carbon steel can be seen in Figure 3a. The bright area is pro-eutectoid ferrite, and the dark area is pearlite [24][25][26]. Because the carbon content of the steel is less than 0.77 wt.%, ferrite will be precipitated along the austenite grain boundary before the pearlite transformation.…”

Microstructure Evolution during Hot Deformation of UNS S32750 Super-Duplex Stainless Steel Alloy

“…The inspection with penetrant liquid was used after cooling to again investigate the samples for fissures/microcracks. A detailed presentation of the thermomechanical processing equipment used is presented in an earlier paper [ 23 ].…”

“…Consequently, the main objectives of this research were the determination of the optimum hot deformation temperatures range of the UNS S32750 SDSS alloy, and the study of the main microstructural changes occurring during hot deformation. The optimal degree of deformation for the UNS S32750 SDSS alloy, was analyzed in a previous paper [ 23 ]. The current paper represents a continuation of these earlier experiments, with the aim of establishing a whole package of optimal, useful, and necessary hot deformation processing parameters.…”