Effects of cerium on the compositional variations in and around inclusions and the initiation and propagation of pitting corrosion in hyperduplex stainless steels

Jeon, Soon-Hyeok; Kim, Soontae; Choi, Min-Seok; Kim, Ji-Soo; Kim, Kwang-Tae; Park, Yong Soo

doi:10.1016/j.corsci.2013.06.020

Cited by 107 publications

(35 citation statements)

References 33 publications

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“…The composition and structure of inclusions determine the mechanism of pitting initiation [ 26 , 27 , 28 ]. In order to verify the pitting process and pitting resistance of the three kinds of inclusions in the X70 steel, specimens’ surfaces after different immersion times were examined by SEM and EDS.…”

Section: Resultsmentioning

confidence: 99%

Pitting Initiation and Propagation of X70 Pipeline Steel Exposed to Chloride-Containing Environments

Yang

Kan

et al. 2017

Materials

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Inclusion-induced pitting initiation mechanisms in X70 steel were investigated by scanning electron microscopy, scanning Kelvin probe force microscopy (SKPFM), immersion and electrochemical polarization tests in chloride-containing ion solutions. There are three inclusion types in the X70 steel. Corrosion test results indicated that pitting corrosion resistance of type A inclusion < type C inclusion < type B inclusion, i.e., (Mn, Ca)S < matrix < (Al, Ca)O. SKPFM test results show that the type A inclusion exhibited both lower and higher potentials than the matrix, while the type B inclusion exhibited higher potential than the matrix. The corrosion test and the SKPFM potential test results are consistent. Potentiodynamic polarization results indicate that the type A and C are active inclusions, while the type B is an inactive inclusion. Three kinds of possible mechanisms of inclusion-induced pitting corrosion are established for the X70 steel.

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Section: Resultsmentioning

confidence: 99%

Pitting Initiation and Propagation of X70 Pipeline Steel Exposed to Chloride-Containing Environments

Yang

Kan

et al. 2017

Materials

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“…Moreover, the addition of a small amount of Gd with an undisclosed SDSS deoxidizing capacity resulted in a substantial change in the oxide content. Thermodynamically, REM-based oxides or oxysulfides are stable compounds owing to their formation of low standard free energies [58]. The standard Gibbs free energy formation for Gd 2 O 3 is −2457 kJ/mol is larger than those for MnO, Cr 2 O 3 , and SiO 2 .…”

Section: Characterization Of Inclusionsmentioning

confidence: 99%

The Effect of Gadolinium on the Microstructures and Charpy Impact Properties of Super Duplex Stainless Steels

Moon

Lee

Kim

et al. 2018

Metals

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Super duplex stainless steels (SDSSs), exhibiting excellent strength and corrosion resistance, serve as the attractive materials in a variety of industries. However, improvements in their ductility and impact-toughness are required in extreme environments. In this study, the effects of gadolinium on the microstructures and Charpy impact properties of super duplex stainless steels were investigated. A base super duplex stainless steel (BDSS) and a gadolinium-added super duplex stainless steel (GDSS) were successfully fabricated using an air casting method. The oxygen content and grain size of SDSSs were found to decrease because of high reactivity of gadolinium with oxygen. Moreover, the average inclusion size and area of GDSS also decreased even with a slight decrease in the average distance between inclusions. Both the BDSS and GDSS exhibited typical Charpy impact transition behavior from −196 • C to 200 • C. Moreover, the GDSS impact energies using Charpy test were higher than those of BDSS over the entire temperature range. Moreover, the ductile-to-brittle transition temperature (DBTT) of SDSSs calculated from the fracture appearance transition temperature (FATT) significantly decreased by over 20 • C with the addition of gadolinium.

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“…With the increasing demand for high-performance stainless steel, rare earth metals (REM), such as cerium, lanthanum, and yttrium, have been extensively applied in the steel manufacturing process. It has been reported that the addition of REM to stainless steel can significantly improve its corrosion resistance and mechanical properties such as strength, hot ductility, toughness, and oxidation resistance [1][2][3][4][5]. There are three main functions for REM in steel: modifying inclusions, deeply purifying molten steel, and alloying [6].…”

Section: Introductionmentioning

confidence: 99%

Transformation of Oxide Inclusions in Stainless Steel Containing Yttrium during Isothermal Heating at 1473 K

Zhang

Yang

et al. 2019

Metals

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To provide fundamental information on the control of rare earth inclusions in solid steel, two 18 mass% Cr-8 mass% Ni stainless steels with different yttrium additions were prepared using an electric resistance furnace and the evolution of yttrium-based oxide inclusions during heat treatment of the steels at 1473 K was investigated. In both as-cast steels, homogeneous spherical Al-Y-Si(-Mn-Cr) oxide inclusions were observed; however, the steel with larger yttrium additions also had some heterogeneous oxide inclusions with double phases. After heating, a new oxide phase with higher yttrium content precipitated from the original inclusions and resulted in partitioning to Y-rich and Al-rich parts in both steels. The average size and number density of inclusions slightly increased, and the morphology of inclusions changed from spherical to irregular. The transformation mechanism during isothermal heating was proposed to be the mutual effects of (i) internal transformation of the yttrium-based inclusions owing to crystallization of glassy oxide and (ii) interfacial reaction between inclusions and the steel matrix.Metals 2019, 9, 961 2 of 15 morphology of inclusions changed from dendritic to globular. A similar result was also observed by Katsumata et al. in 25 mass% Cr-6 mass% Ni stainless steel [8]. Kwon et al. [9,10] investigated the evolution of inclusions in Al-killed stainless steel with Ce addition at 1873 K. Mn(Cr)-silicates were found to be the primary inclusions before Al addition. When Al was added without Ce addition, the initial Mn(Cr)-silicate changed to Al 2 O 3 -rich inclusions. Then, Al-Ce complex inclusions were formed in the steel after Ce addition due to the reaction between Ce and Al 2 O 3 particles. Jönsson et al. [11,12] investigated the three-dimensional characteristics of clusters in REM-alloyed (Ce, La, Pr, and Nd) stainless steel through an electrolytic extraction method. It was found that most of the REM cluster consisted of regular and irregular REM-oxides, and the size of these clusters varied in the range of 2 to 23 µm. Moreover, turbulent collisions were determined to be the dominant form for the growth of REM clusters. With increasing the size of clusters, the growth rate of REM clusters increased.The changing behavior of rare earth inclusions in molten steel is relatively clear now; however, less attention has been paid to the possible transformation of rare earth inclusions in solid steel during heat treatment. This is practically important because steel quality significantly depends on the final state of inclusions after different thermal and mechanical treatments [13]. Many researchers have reported that some inclusions would change during heat treatment [14][15][16][17][18][19][20][21]. In 18 mass% Cr-8 mass% Ni austenitic stainless steel, MnO-SiO 2 oxide inclusions changed to finer MnO-Cr 2 O 3 spinel during heat treatment at 1473 K due to the interfacial reaction between inclusions and steel matrix [14][15][16][17][18]. Grain growth during heat treatment was also suppressed effec...

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Effects of cerium on the compositional variations in and around inclusions and the initiation and propagation of pitting corrosion in hyperduplex stainless steels

Cited by 107 publications

References 33 publications

Pitting Initiation and Propagation of X70 Pipeline Steel Exposed to Chloride-Containing Environments

Pitting Initiation and Propagation of X70 Pipeline Steel Exposed to Chloride-Containing Environments

The Effect of Gadolinium on the Microstructures and Charpy Impact Properties of Super Duplex Stainless Steels

Transformation of Oxide Inclusions in Stainless Steel Containing Yttrium during Isothermal Heating at 1473 K

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