The Influence of Grain Size and Certain Precipitate Parameters on the Creep Properties of Ni-Cr-Base Alloys

Gibbons, T. B.; Hopkins, B. E.

doi:10.1179/030634571790439478

Cited by 41 publications

(6 citation statements)

References 3 publications

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“…However, this is consistent with the higher solvus temperature of 740H. The average γ́ particle diameter and its variation over time is a key factor in creep strength of age-hardened nickel alloys [21]. Since other microstructural changes do not occur in 740H, a measurement of γ́ size may provide a useful indicator of residual life.…”

Section: Microstructure Stabilitysupporting

confidence: 58%

Microstructure Stability of Alloy 740H and its Effect on Material Properties

Barbadillo¹,

Baker²,

Xie

2014

ASME 2014 Symposium on Elevated Temperature Application of Materials for Fossil, Nuclear, and Petrochemical Industries

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Alloy 740H was developed specifically for boiler tube and steam transfer pipe for the Advanced-Ultrasupercritical steam boiler application. The composition was formulated to provide creep strength, weldability and oxidation and coal ash corrosion resistance. It is the first nickel-base age-hardened alloy to be approved under Section 1 of the ASME Boiler and Pressure Vessel Code. Although a significant amount of microstructure and creep data was submitted to support the code case, it was largely collected on tube and light plate, much of this from pilot-scale material. The data package did not cover other product forms, sizes, hot working methods and weld joint configurations that may be required to construct a power plant. These include large diameter pipe, bends, fittings, heavy section welds, dissimilar metal welds, etc. that have complex thermal cycles and composition gradients. An ongoing effort is underway to characterize the microstructure and properties of alloy 740H under a range of manufacturing processes and to project these results through the potential life cycle of a plant. This paper describes the current status of this work. Paper published with permission.

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Section: Microstructure Stabilitysupporting

confidence: 58%

Microstructure Stability of Alloy 740H and its Effect on Material Properties

Barbadillo¹,

Baker²,

Xie

2014

ASME 2014 Symposium on Elevated Temperature Application of Materials for Fossil, Nuclear, and Petrochemical Industries

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“…[7,8] Because of the extremely brittle property of MC carbides, they may act as crack initiation sites and propagation paths. [6,9] In order to minimize these detrimental effects, refinement and modification of coarse MC carbides through processing or microalloying are thought to be desirable and effective.…”

mentioning

confidence: 99%

The effects of Mg microaddition on the mechanical behavior and fracture mechanism of MAR-M247 superalloy at elevated temperatures

Bor

Chao

1999

Metall Mater Trans A

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The effects of microadditions of Mg on the mechanical behavior and fracture mechanism of MAR-M247 superalloy were investigated in this study. The microstructural observations and image analysis showed that a Mg microaddition ranging from 30 to 80 ppm significantly changed the primary MC carbide characteristics and inhibited the scriptlike carbide formation. After a 80 ppm Mg addition, the elongation measured at 1172 K increased over 3 times found that for the Mg-free MAR-M247 superalloy. The creep life and rupture elongation of the MAR-M247 superalloy with 80 ppm Mg was also improved up to 3 to 5 times that of the alloy without Mg during a 1033 K/724 MPa creep test. The fracture analyses demonstrated that cracks were mainly initiated and propagated at the interface of scriptlike MC carbides in the Mg-free MAR-M247 superalloy at elevated temperatures. The Mg microaddition effectively refined and spheroidized these coarse carbides so that a change in the crack initiation occurred from the carbide/matrix interface to that along the ␥-␥' eutectic. Interfacial analysis using Auger electron spectroscopy illustrated that Mg segregated to the interface of the MC carbide/matrix, causing a change in the morphology and interfacial behavior of the carbides. This improvement contributed to a prolonged rupture life and upgraded the moderate temperature ductility of the MAR-M247 superalloy.

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“…Numerous papers44 – 48 have taken a broader look at the creep process, some renewing the search for strain–time relationship in creep, the onset of failure and the prediction of creep life 49. Studies of this kind have been made on materials similar or close to those envisaged for commercial application,17,50 – 55 pointing the way towards useful further alloy development. These, more general approaches have been reported alongside more specific studies focusing, as far as possible, on the endeavour to identify individual relationships.…”

Section: Reflections On Creep: a Review Of The Mst Archivementioning

confidence: 99%

Reflections on creep: A review of the mst archive

2013

Materials Science and Technology

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Amongst many themes embedded in Materials Science and Technology (MST), the phenomenon of creep has remained a significant component, seamlessly continuing from the journals through which MST was directly descended. The Journal of the Iron and Steel Institute (JISI), from its founding in 1869, recorded procedures to manufacture steels to withstand arduous conditions to improve the performance of furnaces and engines. The problem of creep was identified and its exploration included its occurrence in non-ferrous metals and alloys with results on these published in the Journal of the Institute of Metals (JIM). The sensitivity of creep to materials' processing as well as to chemical composition was soon apparent. The brief commentary here outlines some of the main features in this area as reported by the successive line of journals, but it gives no more than a taste the wealth of information, ideas and proposals they contain.Early studies were necessarily empirical but became more focused by progressively controlling parameters that led to variable results. The shape of the strain versus time curve at constant uniaxial stress and temperature was a prominent consideration with formulae proposed for its description. 1 Such attention has continued with increasing sophistication 2 aided by the data processing power of computers. Experimental results and the capability of their extrapolation are vital ingredients in attempting to make realistic prediction of long term behaviour to times greatly in excess of those feasible in laboratory testing. Within relatively narrow ranges of material composition and microstructure and of imposed conditions such efforts have made valuable progress but the high sensitivity of the creep process to both internal and external variables indicates that unique relationships to cover a wider range of conditions are unlikely to emerge in a simple, precise and accurate form.Many contributions have aimed at interpretation of creep behaviour. [16][17][18][19] These were aided by substantial support for basic scientific research in the post-war years that encouraged studies 20-24 on metals with well characterised microstructures and accurately known levels of impurity. Much of this work was nevertheless driven by practical and commercial needs, urgently seeking data and better understanding of the behaviour of materials under severe conditions and in entirely new environments such as those inherent in nuclear power generation. Papers concerned with these areas have necessarily invoked extensive understanding of broad areas of metallurgy. As well as enhancing surface reactions, elevated temperatures allow precipitates to coarsen, grain boundaries to migrate and shear, impurities to segregate, dislocations to climb as well as glide, vacancies to be created, diffuse, condense and be absorbed.

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The Influence of Grain Size and Certain Precipitate Parameters on the Creep Properties of Ni-Cr-Base Alloys

Cited by 41 publications

References 3 publications

Microstructure Stability of Alloy 740H and its Effect on Material Properties

Microstructure Stability of Alloy 740H and its Effect on Material Properties

The effects of Mg microaddition on the mechanical behavior and fracture mechanism of MAR-M247 superalloy at elevated temperatures

Reflections on creep: A review of the mst archive

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