Creep Mechanisms in Niobium-Stabilized Austenitic Steels

Russell, B.; Ham, Robert K.; Silcock, J. M.; Willoughby, G.

doi:10.1179/030634568790443242

Cited by 31 publications

(5 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…3 shows that the creep results are of the general form found for this type of stainless steel [15,22]. Over the majority of the stress range, the results can be fitted to a power law dependence, i.e.…”

Section: Discussionmentioning

confidence: 92%

The recovery creep of niobium-stabilised austenitic stainless steels

Williams

McLauchlin

1970

J Mater Sci

View full text Add to dashboard Cite

The creep properties of niobium-stabilised stainless steels of carbon contents in the range 0.01 to 0.05% carbon can be accounted for by the general recovery theory of creep. The high stress dependencies of recovery and creep rate can be adequately explained through an internal friction stress or impedance term, retarding recovery. Measurement of this friction term by dislocation density and stress relaxation techniques provides the correct stress dependencies when applied to the modified recovery theory. t. IntroductionThe recovery theory of creep is based on the knowledge that metals harden with strain, and soften with time on heating [1,2]. During steady state creep, it was postulated that there will be an exact balance between strain-hardening and recovery, such that the steady state creep rate is given by McLean et al [4][5][6][7] who have shown that the above relation is a general one and holds for pure metals and single phase alloys. More recent work on these materials has shown that the theory can be extended into the primary and tertiary stages of creep with equal success [8][9][10][11].The theories of McLean et al [4][5][6][7] although very attractive due to their inherent simplicity, are not generally applicable to high-strength particle-hardened material. In general they suffer from an inability to predict the high stress dependence of the recovery and creep rates found in such materials, although McLean [7] has shown in principle the way in which this discrepancy arises. In addition, it has been found difficult to test the recovery theory on materials containing second phase particles, as it is often not easy and sometimes impossible [12] McLean's theories [4][5][6][7] assume that the dislocations formed during creep exist in a threedimensional network, and that the growth of such a network, essentially by climb of dislocations, constitutes the recovery process. If the average mesh size of the network is x, the driving force for recovery is inversely proportional to x [13] and the growth rate of the average network size is given by dx M. Todt x where M = mobility factor and TD = line tension of the dislocation. This treatment is analogous to that applied to normal grain growth, and the influence of particles in retarding the growth rate [14] can be applied in a similar manner. Lagneborg [15] has introduced an impedance factor, Z, into equation 2 such that Z depends both on the number and size of the impeding particles, and on the nature of the particle-dislocation interaction. A growing network will thus experience a retarding force

show abstract

Section: Discussionmentioning

confidence: 92%

The recovery creep of niobium-stabilised austenitic stainless steels

Williams

McLauchlin

1970

J Mater Sci

View full text Add to dashboard Cite

show abstract

“…Many contributions have aimed at interpretation of creep behaviour 16 – 19. These were aided by substantial support for basic scientific research in the post-war years that encouraged studies20 – 24 on metals with well characterised microstructures and accurately known levels of impurity.…”

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

confidence: 99%

“…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.…”

mentioning

confidence: 99%

“…[16][17][18][19] These were aided by substantial support for basic scientific research in the post-war years that encouraged studies [20][21][22][23][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.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Reflections on creep: A review of the mst archive

2013

Materials Science and Technology

View full text Add to dashboard Cite

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.

show abstract

“…These provide high temperature strength by acting as obstacles for moving dislocations. 3,4 The objective of this work is to investigate the creep behaviour of the current HP modified microalloyed (HP-Mod) alloy which, although widely used for its creep properties, has not had these particularly well characterised. The current experimental results will show that the creep life is dominated by the tertiary stage, with an absence of steady state creep, even under conditions of constant tensile stress.…”

Section: Introductionmentioning

confidence: 99%

Origins of tertiary creep in microalloyed 25Cr–35Ni centrifugally cast alloy tubes

Nowak

Evans

Connolly

et al. 2014

Materials at High Temperatures

View full text Add to dashboard Cite

Constant stress tensile creep tests have been undertaken in air on as cast 25Cr35Ni austenitic steel at temperatures of 880, 900 and 950uC. The creep curves were found to consist of a relatively short primary stage, a minimum strain rate and an extended tertiary stage. There was no convincing evidence of a period of steady-state creep but the minimum creep rate was found to be highly dependent on applied stress through a power law with a stress exponent of~10. The early occurrence of tertiary creep, after strains of only~0?01, was shown not to be caused by a loss of section associated with necking, internal void development nor with the formation of surface cracks. It is concluded that the most likely cause of the early onset of tertiary creep in this alloy is the coarsening of strengthening precipitates.

show abstract

Creep Mechanisms in Niobium-Stabilized Austenitic Steels

Cited by 31 publications

References 8 publications

The recovery creep of niobium-stabilised austenitic stainless steels

The recovery creep of niobium-stabilised austenitic stainless steels

Reflections on creep: A review of the mst archive

Origins of tertiary creep in microalloyed 25Cr–35Ni centrifugally cast alloy tubes

Contact Info

Product

Resources

About