Precipitation of M23C6 in austenitic steels

Lewis, M. H.; Hattersley, B.

doi:10.1016/0001-6160(65)90053-2

Cited by 248 publications

(76 citation statements)

References 5 publications

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“…Note that this is not unreasonable given the identification of intragranular M 23 C 6 after 30 min at 750°C. 17) Assuming a spherical shape, the volume increment during a time step is given by: where N is the number density of particles, given by N v 1/3 L d where N v is the number of atoms per unit volume and L d the dislocation density. 10) dr is estimated from the interface velocity.…”

Section: Influence Of Intragranular Precipitationmentioning

confidence: 99%

Sensitisation and Evolution of Chromium-depleted Zones in Fe-Cr-Ni-C Systems

2003

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The development of chromium concentration profiles in austenitic stainless steels, due to the grain boundary precipitation of carbides has been modelled, taking account of multicomponent effects, both in the estimation of the state of equilibrium at the carbide/matrix interface and in diffusion. A comparison against published experimental data shows that the theory accounts for the development of the depleted zone as well as self-healing, unlike recent work where these effects are treated as separate phenomena. At the same time, the present model preserves local equilibrium at the precipitate-matrix interface and provides a natural explanation for the observation of delays in reaching the minimum chromium content.

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Section: Influence Of Intragranular Precipitationmentioning

confidence: 99%

Sensitisation and Evolution of Chromium-depleted Zones in Fe-Cr-Ni-C Systems

2003

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“…In general, no simple description based on a single morphology seems appropriate .for grain boundary carbides. Detailed study of this subject by Wilson et al found a variety of carbides shaped as dendritic rods, lace-like sheets, or coarsened spheroids among others which all coexist in the same material (113,114,115,116). These morphologies were also observed in the present study.…”

Section: Crack-like Cavitiesmentioning

confidence: 99%

Creep cavitation in 304 stainless steel

Chen¹,

Argon²

1981

Acta Metallurgica

183

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A micromechanical analysis of deformation and fracture in creeping alloys is presented based on a mechanistic approach using continuum mechanics. The analysis was first carried out on a coarse microscopic level in which the self-consistent theory of Hill was employed to treat the steady state creep of heterogeneous alloys with coarse microstructures allowing for grain boundary sliding. Processes operating on a finer scale than the grain size such as grain boundary diffusion and surface diffusion were subsequently included in the analysis. It was found that the high stresses required for cavity nucleation occur at intergranular particles only in transients of grain boundary sliding, and that two modes of cavity growth result corresponding to rate control by each of the abovementioned diffusional processes.Creep cavitation in 304 stainless steel in the neighborhood of 0.5 Tm was studied experimentally to test these theoretical models. Our results suggest that a broad spectrum of interfacial energy may exist and that microstructural changes such as those caused by twins can alter cavitation behavior drastically. Cavities grow in most cases by grain boundary diffusion coupled with matrix creep, somewhat restricted by surface diffusion. However, the grain boundary sliding can be a dominant mode of cavity growth at high stresses and for large cavities.

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“…• C in an austenitic stainless steel [31]. It can be located in grain boundaries (GBs) [30,31], twin boundaries (TBs) [32][33][34] and intragranular sites [30,32].…”

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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Precipitation of M23C6 in austenitic steels

Cited by 248 publications

References 5 publications

Sensitisation and Evolution of Chromium-depleted Zones in Fe-Cr-Ni-C Systems

Sensitisation and Evolution of Chromium-depleted Zones in Fe-Cr-Ni-C Systems

Creep cavitation in 304 stainless steel

On High-Temperature Behaviours of Heat Resistant Austenitic Alloys

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