Long-term creep data prediction for type 316H stainless steel

Whittaker, Mark; Evans, Mark; Wilshire, B.

doi:10.1016/j.msea.2012.05.023

Cited by 53 publications

(50 citation statements)

References 7 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A wide range of materials [24,25,26,27] have now been studied for which optimised fits are obtained when the value of the apparent activation energy (Q c *) is allowed to vary either side of the break point. Interestingly, the most significant changes in the apparent activation energy observed have been in stainless steel grade 316, with values of 250 kJ/mol observed above the yield stress, decreasing to 150 kJ/mol below.…”

Section: Introductionmentioning

confidence: 99%

Creep Deformation by Dislocation Movement in Waspaloy

et al. 2017

View full text Add to dashboard Cite

Creep tests of the polycrystalline nickel alloy Waspaloy have been conducted at Swansea University, for varying stress conditions at 700 °C. Investigation through use of Transmission Electron Microscopy at Cambridge University has examined the dislocation networks formed under these conditions, with particular attention paid to comparing tests performed above and below the yield stress. This paper highlights how the dislocation structures vary throughout creep and proposes a dislocation mechanism theory for creep in Waspaloy. Activation energies are calculated through approaches developed in the use of the recently formulated Wilshire Equations, and are found to differ above and below the yield stress. Low activation energies are found to be related to dislocation interaction with γ′ precipitates below the yield stress. However, significantly increased dislocation densities at stresses above yield cause an increase in the activation energy values as forest hardening becomes the primary mechanism controlling dislocation movement. It is proposed that the activation energy change is related to the stress increment provided by work hardening, as can be observed from Ti, Ni and steel results.

show abstract

Section: Introductionmentioning

confidence: 99%

Creep Deformation by Dislocation Movement in Waspaloy

et al. 2017

View full text Add to dashboard Cite

show abstract

“…The extent of dislocation interaction during the high stress regime of any material in creep is reflected in the rate of strain hardening of a material observed during monotonic tensile tests. There is a strong relationship between the apparent activation energy and the amount of strain hardening a material undergoes after yield, as evidenced by three model materials; 316 stainless steel has a very high rate of strain hardening and shows Q * c values of 250/150 k J/mol [12], Waspaloy has a medium rate of strain hardening with Q * c values of 400/340 kJ/mol and titanium 6-4 has a very low rate of strain hardening with negligible activation energy change, having Q * c values of 250/250 kJ/mol [13]. This supports the proposal that activation energy change in creep is a direct result of the increment of strain hardening: an alloy with no potential for strain hardening would not be expected to show a change in activation energy.…”

Section: Discussionmentioning

confidence: 99%

Relating fundamental creep mechanisms in Waspaloy to the Wilshire equations

Deen

Whittaker

Harrison

et al. 2014

MATEC Web of Conferences

Self Cite

View full text Add to dashboard Cite

Abstract. Creep tests of the polycrystalline nickel alloy Waspaloy have been conducted at Swansea University, for varying stress conditions at 700 • C. Investigation through use of Transmission Electron Microscopy at Cambridge University has examined the dislocation networks formed under these conditions, notably those with stresses above and below the yield stress. This paper highlights how the dislocation structures vary throughout creep and proposes a dislocation mechanism theory for creep in Waspaloy. In particular, the roles of recovery, tertiary gamma prime particles and dislocation foresting are examined, and related back to observations from the Wilshire fits. The virgin (untested) material has been forged and heat treated, containing some recrystallised material together with areas of more heavily deformed and recovered material clustered around the grain boundaries. Observations from tests below the 0.2% proof stress show relatively low dislocation densities away from grain boundaries and dislocation movement can be seen to be governed by interactions with the γ precipitates. In contrast, above the 0.2% proof stress, TEM observations show a substantially greater density of dislocations. The increased density provides an increment of strength through forest hardening. At stresses above the original yield point, determined by the precipitates, the creep rate is controlled by inter-action with the dislocation forest and results in an apparent activation energy change. It is proposed that the activation energy change is related to the stress increment provided by work hardening, as can be observed from Ti, Ni and steel results.

show abstract

“…The aim of this new approach is to use limited experimental rupture data to calculate the correct creep rupture stress. The interpolation and extrapolation on creep rupture experimental data is a challenging field, on which many other researchers (Larson and Miller, 1952;Manson and Haferd, 1953;Mendelson et al, 1965;Pink, 1994;Whittaker et al, 2012) worked to produce reliable long term creep rupture data. In order to interpolate and extrapolate creep rupture data required for the LMM creep rupture analysis, different approaches and strategies are investigated.…”

Section: Numerical Schemes On Creep Rupture Stress Using Limited Expementioning

confidence: 99%