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.
Highlights
Super Duplex Stainless Steels (SDSS) are known to exhibit high mechanical and corrosion resistance properties, which recommend them to be used in hard exploitation conditions, such as those encountered in oil, chemical, marine and nuclear industrial fields [1,2,3,4,5,6,7,8]
The microstructural evolution of SDSS after hot deformation and subsequent solution annealing is very important for preventing the formation of deleterious intermetallic phases and, the easiest solution to achieve the desired properties seems to be a proper control of thermo-mechanical treatment Metals
The microstructure of SDSS alloys usually contain a mixture of primary phases, such as δ-Fe and γ-Fe, and other secondary phases, such as: σ (Cr-Fe), χ, Cr2 N
Summary
Super Duplex Stainless Steels (SDSS) are known to exhibit high mechanical and corrosion resistance properties, which recommend them to be used in hard exploitation conditions, such as those encountered in oil, chemical, marine and nuclear industrial fields [1,2,3,4,5,6,7,8]. The microstructural evolution of SDSS after hot deformation and subsequent solution annealing is very important for preventing the formation of deleterious intermetallic phases and, the easiest solution to achieve the desired properties seems to be a proper control of thermo-mechanical treatment Metals [21,22,23,24,25]. N) and hot deformation subsequent solution annealing is very for preventing the the corrosion resistance formation of each phase [1,26] In this regard, studying the correlation theachieve solution of deleterious intermetallic phases and, the easiestbetween solution to the treatment desired properties seems tocharacteristics be a proper control of thermo-mechanical treatment [21,22,23,24,25]. Component phases in different conditions of thermo-mechanical processing were identified and characterized by means of SEM-BSE (Scanning Electron Microscopy-Backscattered Electrons) and
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