The growth of M23C6 carbide on incoherent twin boundaries in austenite

Singhal, L. K.; Martin, J.W.

doi:10.1016/0001-6160(67)90134-4

Cited by 60 publications

(12 citation statements)

References 7 publications

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“…M 23 C 6 was found at numerous sites: a strong presence on grain boundaries, with a globular morphology, on incoherent and coherent twin boundaries (ITB and CTB, respectively) with a plate morphology, and around residual NbN precipitates. All these occurrences are well documented and have been reported on numerous occasions (for example, Lewis and Hattersley, [6] Beckitt and Clarck, [7] Singhal and Martin, [8] and Adamson and Martin [9] ), with the exception of the formation of plates around residual NbX particles. [1] M 23 C 6 has a cube-to-cube orientation relationship with the austenite, and its lattice parameter is 3 times that of the matrix; typical diffraction patterns appear, as shown in Figures 5(d) and (f).…”

Section: A Tem Identification Of the Phases Present In Nf709mentioning

confidence: 82%

Microstructural evolution in two variants of NF709 at 1023 and 1073 K

Sourmail

Bhadeshia

2005

Metall Mater Trans A

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The microstructural state of two grades of the creep-resistant austenitic stainless steels NF709, a Fe20Cr-25Ni (wt pct) based steel, has been studied, in the as-received state, after an additional solution treatment and after static aging at 1023 and 1073 K. Although the two variants are chemically similar, they exhibit different microstructures following identical heat treatment. In particular, the Z phase and are found in largely different quantities. The study suggests that a seldom observed variant of the structure, Cr 3 Ni 2 SiX, is stabilized by nitrogen. Both steels exhibit a yet undocumented precipitation sequence when compared to more conventional austenitic steels (for which the precipitation sequences have been reviewed by Sourmail (Mater.

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Section: A Tem Identification Of the Phases Present In Nf709mentioning

confidence: 82%

Microstructural evolution in two variants of NF709 at 1023 and 1073 K

Sourmail

Bhadeshia

2005

Metall Mater Trans A

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“…The good matching crystallographic direction between the matrix and M 23 C 6 is the h1 1 0i directions on {1 1 1} planes [5,31]. Therefore the chromium-rich M 23 C 6 grows in the h110i direction on {1 1 1} plane.…”

Section: The Dependence Of Carbide Morphology On Grain Boundary Charamentioning

confidence: 97%

“…However, if M 23 C 6 bars could form by the repeated nucleation on a migrating dislocation, such bars might have been commonly observed elsewhere in the matrix, because M 23 C 6 also nucleate on dislocations inside grains. According to the work of Singhal and Martin [31], stacking faults are created by the gliding of dislocations from the incoherent twin boundary. M 23 C 6 grows across the faults forming bars.…”

Section: The Morphology Of Carbides Precipitated At Incoherent Twin Bmentioning

confidence: 99%

“…Because of the low interface energy of incoherent twin boundary and twin related R9 grain boundary, the carbide dendrites grow not only on grain boundary, but also into the sideward matrix. The bar-like carbide dendrites grow with axes parallel to the h1 1 0i directions on {1 1 1} planes due to the good matching in the h1 1 0i directions on {1 1 1} planes between the matrix and M 23 C 6 [5,31]. One nature of dendrites is that the growth directions of the same order dendrites are parallel to each other, so the carbide bars are parallel to each other (Figs.…”

Section: The Morphology Of Carbides Precipitated At Incoherent Twin Bmentioning

confidence: 99%

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The dependence of carbide morphology on grain boundary character in the highly twinned Alloy 690

Xia

Zhou

et al. 2010

Journal of Nuclear Materials

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“…It can be located in grain boundaries (GBs) [30,31], twin boundaries (TBs) [32][33][34] and intragranular sites [30,32]. M 23 C 6 most often appears in GBs where it may control the nucleation of creep cavities [30] and is often connected to intergranular corrosion due to depletion of chromium at GBs [13,35,36].…”

Section: Carbides and Nitridesmentioning

confidence: 99%

On High-Temperature Behaviours of Heat Resistant Austenitic Alloys

Calmunger¹

2015

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Advanced heat resistant materials are important to achieve the transition to long term sustainable power generation. The global increase in energy consumption and the global warming from greenhouse gas emissions create the need for more sustainable power generation processes. Biomass-fired power plants with higher efficiency could generate more power but also reduce the emission of greenhouse gases, e.g. CO 2 . Biomass is the largest global contributor to renewable energy and offers no net contribution of CO 2 to the atmosphere. To obtain greater efficiency of power plants, one option is to increase the temperature and the pressure in the boiler section of the power plant. Raised temperature and pressure increase the demands of the operating materials of the future high-efficient biomass-fired power plants. This requires improved properties, such as higher yield strength, creep strength and high-temperature corrosion resistance, as well as structural integrity and safety. Also, the number of start-and-stop cycles will increase, leading to demands on increased material performance under cyclic loading, both from thermal and mechanical loads.Heat resistant austenitic alloys, such as austenitic stainless steels and nickelbased alloys, possess excellent mechanical and chemical properties at the elevated temperatures and cyclic loading conditions of today's biomass-fired power plants. Today, some austenitic stainless steels are design to withstand temperatures up to 650• C in tough environments. Nickel-based alloys are designed to withstand even higher temperatures. Austenitic stainless steels are more cost effective than nickel-based alloys due to a lower amount of expensive alloying elements. However, the performance of austenitic stainless steels at the elevated temperatures of future operation conditions in biomassfired power plants is not yet fully understood.This thesis presents research on the influence of long term high-temperature ageing on mechanical properties, the influence of very slow deformation rates at high-temperature on deformation, damage and fracture, and the influence iii of high-temperature environment and cyclic operation conditions on the material behaviour. The research has been conducted on several commercial heat resistant austenitic alloys. Mechanical testing, such as impact toughness tests, uniaxial tensile tests at elevated temperatures using various strain rates and creep-fatigue interaction tests, has been performed. Also, thermal testing such as long term ageing and thermal cycling in a water vapour environment has been performed. The mechanical and thermal testing have been followed by subsequent studies of the microstructure, using scanning electron microscopy, to investigate the deformation, damage and fracture mechanisms as well as the precipitation and corrosion behaviours.Results shows that long term ageing (up to 10 000 hours) at high temperatures (up to 700• C) leads to the precipitation of intermetallic phases. These intermetallic phases are brittle at room temperatu...

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The growth of M23C6 carbide on incoherent twin boundaries in austenite

Cited by 60 publications

References 7 publications

Microstructural evolution in two variants of NF709 at 1023 and 1073 K

Microstructural evolution in two variants of NF709 at 1023 and 1073 K

The dependence of carbide morphology on grain boundary character in the highly twinned Alloy 690

On High-Temperature Behaviours of Heat Resistant Austenitic Alloys

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