Microstructural evolution and mechanical properties of 27Cr-4Mo-2Ni ferritic stainless steel during isothermal aging

Lu, Hui-Hu; Luo, Yi; Guo, Hong-Kui; Li, Wenqi; Li, Jianchun; Liang, Wei

doi:10.1016/j.msea.2018.08.031

Cited by 45 publications

(14 citation statements)

References 23 publications

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“…It precipitates as fine particles along the ferrite grain boundaries and does not significantly grow due to the start of precipitation of r phase and the exhaustion of the available Nb [785,787]. Similar observations were made in 27Cr-4Mo-2Ni superferritic steel after hot rolling, solution treatment at 1050°C and/or aging between 600 and 800°C [789][790][791][792]. Increased Cr contents were found to promote the precipitation of r and Laves phase and to widen the precipitation temperature region of the Laves phase, but annealing at temperatures above 1000°C can result in complete dissolution of the detrimental phases [788].…”

Section: Superferritic Steels (C 25% Cr)supporting

confidence: 69%

“…At higher temperatures, detrimental embrittling intermetallic phases such as r (FeCr), v (Fe 36 Cr 12 M 10 ), and Laves phase (Mo,Nb,Ti)Fe 2 can precipitate. Due to the high Cr contents, the Cr-rich r phase is the most frequently observed precipitating phase, while the occurrence of Laves phase has only rarely been described [784][785][786][787][788][789][790][791][792][793]. In a typical superferritic alloy of composition 25Cr-(2-3)Mo-4Ni containing 0.3 wt% Nb, Laves phase was found to nucleate as first intermetallic phase during aging at 850°C.…”

Section: Superferritic Steels (C 25% Cr)mentioning

confidence: 99%

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Laves phases: a review of their functional and structural applications and an improved fundamental understanding of stability and properties

2020

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Laves phases with their comparably simple crystal structure are very common intermetallic phases and can be formed from element combinations all over the periodic table resulting in a huge number of known examples. Even though this type of phases is known for almost 100 years, and although a lot of information on stability, structure, and properties has accumulated especially during the last about 20 years, systematic evaluation and rationalization of this information in particular as a function of the involved elements is often lacking. It is one of the two main goals of this review to summarize the knowledge for some selected respective topics with a certain focus on non-stoichiometric, i.e., non-ideal Laves phases. The second, central goal of the review is to give a systematic overview about the role of Laves phases in all kinds of materials for functional and structural applications. There is a surprisingly broad range of successful utilization of Laves phases in functional applications comprising Laves phases as hydrogen storage material (Hydraloy), as magneto-mechanical sensors and actuators (Terfenol), or for wear- and corrosion-resistant coatings in corrosive atmospheres and at high temperatures (Tribaloy), to name but a few. Regarding structural applications, there is a renewed interest in using Laves phases for creep-strengthening of high-temperature steels and new respective alloy design concepts were developed and successfully tested. Apart from steels, Laves phases also occur in various other kinds of structural materials sometimes effectively improving properties, but often also acting in a detrimental way.

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Section: Superferritic Steels (C 25% Cr)supporting

confidence: 69%

Section: Superferritic Steels (C 25% Cr)mentioning

confidence: 99%

Laves phases: a review of their functional and structural applications and an improved fundamental understanding of stability and properties

2020

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“…3h. A similar phenomenon has been reported by Lu et al [12], where these precipitates are estimated to be Laves phase. Since a large amount of precipitates are formed at the grain boundaries and grain interiors with aging time, the movement of dislocations and the migration of grain boundaries can be hindered due to the pinning effects of precipitates, thereby suppressing grain growth.…”

Section: Microstructuressupporting

confidence: 87%

“…However, the R s value slightly increases within the aging time, indicating that the erosion ability of the solution is reduced. It is well known that the smaller the value of CPE1, the larger the corrosion resistance [12]. As is shown in Table 3, the value of CPE1 first increases to 5.335 × 10 −5 Ω −1 cm −2 s n and then rapidly decreases with aging time up to 30 h. Therefore, the protective effect of the passive film can be improved by increasing the aging time.…”

Section: Electrochemical Impedance Spectroscopymentioning

confidence: 90%

Influence of Aging Time on Microstructure and Corrosion Behavior of a Cu-Bearing 17Cr–1Si–0.5Nb Ferritic Heat-Resistant Stainless Steel

Zhang

Han

Wen

et al. 2020

Acta Metall. Sin. (Engl. Lett.)

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17Cr-1Si-0.5Nb-1.2Cu ferritic heat-resistant stainless steel was aged at 750 °C from 10 min to 30 h to simulate time aging and study the microstructural evolution and its effect on corrosion behavior by using optical microscopy, scanning electron microscopy, transmission electron microscopy, potentiodynamic polarization, electrochemical impedance spectroscopy, and the Mott-Schottky approach. Four types of precipitates were discovered, including ε-Cu, NbC, Fe 3 Nb 3 C, and Fe 2 Nb-type Laves phase. The nano-sized ε-Cu phase forms first, and its fraction follows the parabolic law change and is the largest. Compared to NbC and Fe 3 Nb 3 C particles, the coarsening of the Laves phase is the most pronounced. The aging process is divided into three parts: early-aged (0-5 h), peak-aged (5 h), and over-aged (5-30 h). However, the corrosion resistance is reduced in the early-aged stage of 0-2 h. Further extending the aging time to 30 h, the corrosion resistance is gradually improved. This change may be related to the competitive relationship between the beneficial effects of the Cu-rich phase and the harmful effects of Nb-containing particles. The dissolved Cu on the surface becomes more effective for the suppression of the anodic dissolution by the formation of ionic compounds of chlorine, thereby reducing the deterioration of corrosion resistance caused by Nb-rich precipitation.

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“…SFSSs contained a high content of Cr and Mo elements with the PRE (pitting resistance equivalent) of more than 38 [24]. While some intermetallic phases were usually precipitated during thermomechanical treatment processes at relatively high temperatures, such as Laves phase, chi phase (χ), and sigma phase (σ) [25]. It was reported that the sigma phase (σ) was composed of Fe and Cr and/or Mo elements, and it formed easily at grain boundaries.…”

Section: Introductionmentioning

confidence: 99%

Microstructure and Properties of Super-Ferritic Stainless Steels Used for Marine Construction after Fire Exposure

Shen

2022

Advances in Materials Science and Engineering

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In this paper, the super-ferritic stainless steels (SFSSs) were simulating treated in a fire accident, and their mechanical properties and corrosion performance before/after fire exposure were studied. The experimental results demonstrated that SFSSs have a good combination property with the tensile strength, total elongation, and corrosion rate in FeCl3 solution of ∼600 MPa, ∼22.5%, and 0.03 mm/a. After fire exposure, the mechanical properties and corrosion performance were affected based on the exposure temperature due to the precipitation of intermetallic compounds. When the fire exposure temperature was 700–800°C, the plasticity was exasperated and the value decreased to only 1.5% at the condition of 800°C × 4 h due to the bulk σ-phase precipitation at grain boundaries. Meanwhile, the brittle fracture patterns emerged, and the corrosion rate in FeCl3 solution increased to 0.4 mm/a. When fire exposure takes place at 600°C for less than 4 h, the mechanical properties and the corrosion performance were little affected. Thus, it was possible to use SFSSs in marine environments.

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Microstructural evolution and mechanical properties of 27Cr-4Mo-2Ni ferritic stainless steel during isothermal aging

Cited by 45 publications

References 23 publications

Laves phases: a review of their functional and structural applications and an improved fundamental understanding of stability and properties

Laves phases: a review of their functional and structural applications and an improved fundamental understanding of stability and properties

Influence of Aging Time on Microstructure and Corrosion Behavior of a Cu-Bearing 17Cr–1Si–0.5Nb Ferritic Heat-Resistant Stainless Steel

Microstructure and Properties of Super-Ferritic Stainless Steels Used for Marine Construction after Fire Exposure

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