“…In fact, the crack propagation in the small punch disc starts in the secondary region of the creep curve instead of the tertiary region, as observed for the typical uniaxial specimen. Figure 12. SEM images from Cortellino et al [49] for a SPCT, for a P91 steel at 600°C with a load of 25 kg, interrupted after (a) 2 h (), (b) 200 h () and (c) after 669 h (), and FE damage contour plots for a P91 steel at 650°C under a load of 200 N, with R s = 1.04 mm and t 0 = 0.5 mm, from Cacciapuoti et al [34]. Figure 13. Creep degradation through life, adapted from Guglielmino et al [114]. …”
Section: Specialised Small Specimen Creep Testingmentioning
The safe operation of components operating at high temperature and pressure faces numerous challenges associated with ageing materials and maintaining commercial viability whilst economies transition to a lower carbon future as part of their climate change commitments. Due to these challenges the plant operator faces increasing pressure to ensure that any capital or operational expenditures are optimised and must ensure that they duly recognise plant age, condition, operating regime and ultimately the planned closure date.This review, for the first time, describes how small specimen creep testing can be applied within a practical and deployable life assessment framework and in conjunction with other assessment techniques. The current state of the art for small specimen creep testing is critically reviewed; this also includes a review of traditional techniques used on site for the metallurgical assessment of material condition, with examples from site investigations and assessment campaigns in both conventional and nuclear plant applications.In order to enhance the current practice for assessing the condition of creep ageing components this review proposes the more proactive use of small specimen testing methods for the in-service condition assessment of power plant materials, notably earlier in the plant lifecycle and within a holistic life assessment framework. This is intended to provide a means of calibrating the time dependent response of the component or system being monitored, thereby providing a key reference in-service strain rate measurement, or material property evaluation, that can subsequently be used with other traditionally deployed assessment methods to define a more targeted and cost-effective forward inspection plan. The review describes how small specimen creep testing methods and other complementary tools can be use in a new and structured approach to life management.The current status of small specimen testing methods, for both conventional and nuclear applications, is described along with a detailed discussion on current practice for in-service creep life assessment, with a case study used to illustrate the main principals. A case study is presented for ageing CMV (0.5%Cr0.5%Mo0.25%V) main steam pipework due to the extensive amount of through life data available, which highlights the particular challenges associated with the interpretation of various types of site outage inspection data, in conjunction with on-load plant operational data. The current approach to the assessment of component condition follows well established inspection based practices defined in various industry good practice guides, with expert elicitation and experience used to judge the condition of the component, system and operational risk on return to service.This review proposes a new approach to the holistic life assessment of high temperature plant, with a particular emphasis on more proactive use of small specimen testing. In addition, the review has 2 highlighted other aspects of the current approach to in-...
“…In fact, the crack propagation in the small punch disc starts in the secondary region of the creep curve instead of the tertiary region, as observed for the typical uniaxial specimen. Figure 12. SEM images from Cortellino et al [49] for a SPCT, for a P91 steel at 600°C with a load of 25 kg, interrupted after (a) 2 h (), (b) 200 h () and (c) after 669 h (), and FE damage contour plots for a P91 steel at 650°C under a load of 200 N, with R s = 1.04 mm and t 0 = 0.5 mm, from Cacciapuoti et al [34]. Figure 13. Creep degradation through life, adapted from Guglielmino et al [114]. …”
Section: Specialised Small Specimen Creep Testingmentioning
The safe operation of components operating at high temperature and pressure faces numerous challenges associated with ageing materials and maintaining commercial viability whilst economies transition to a lower carbon future as part of their climate change commitments. Due to these challenges the plant operator faces increasing pressure to ensure that any capital or operational expenditures are optimised and must ensure that they duly recognise plant age, condition, operating regime and ultimately the planned closure date.This review, for the first time, describes how small specimen creep testing can be applied within a practical and deployable life assessment framework and in conjunction with other assessment techniques. The current state of the art for small specimen creep testing is critically reviewed; this also includes a review of traditional techniques used on site for the metallurgical assessment of material condition, with examples from site investigations and assessment campaigns in both conventional and nuclear plant applications.In order to enhance the current practice for assessing the condition of creep ageing components this review proposes the more proactive use of small specimen testing methods for the in-service condition assessment of power plant materials, notably earlier in the plant lifecycle and within a holistic life assessment framework. This is intended to provide a means of calibrating the time dependent response of the component or system being monitored, thereby providing a key reference in-service strain rate measurement, or material property evaluation, that can subsequently be used with other traditionally deployed assessment methods to define a more targeted and cost-effective forward inspection plan. The review describes how small specimen creep testing methods and other complementary tools can be use in a new and structured approach to life management.The current status of small specimen testing methods, for both conventional and nuclear applications, is described along with a detailed discussion on current practice for in-service creep life assessment, with a case study used to illustrate the main principals. A case study is presented for ageing CMV (0.5%Cr0.5%Mo0.25%V) main steam pipework due to the extensive amount of through life data available, which highlights the particular challenges associated with the interpretation of various types of site outage inspection data, in conjunction with on-load plant operational data. The current approach to the assessment of component condition follows well established inspection based practices defined in various industry good practice guides, with expert elicitation and experience used to judge the condition of the component, system and operational risk on return to service.This review proposes a new approach to the holistic life assessment of high temperature plant, with a particular emphasis on more proactive use of small specimen testing. In addition, the review has 2 highlighted other aspects of the current approach to in-...
“…In the process of controlled rolling and controlled cooling, a large number of fine carbon-nitride precipitation containing Ti, Nb, and V is precipitated and can improve the mechanical properties of steel by postponing the recrystallization and grain growth of austenite grains to refine the grain, as well as by increasing the precipitation strengthening. In addition to ferritic steels, the practice of microalloying is also adopted in the case of austenitic alloys to improve their creep life [17]. Therefore, the microstructure and properties of steel can be effectively improved by controlling the precipitation behavior of Ti, Nb, and V microalloying elements through optimized processing technology [16,18,19].…”
Pipeline steel is a special type of steel used for transporting, for example, oil and natural gas. This study focuses on X80-grade pipeline steel modified with the addition of Nb and Nb-V at different cooling rates (air cooling or quenching) after hot rolling and subjecting it to quenching and tempering heat treatment. Based on multiscale characterization techniques, the effects of microalloying and the cooling rate after hot rolling on the microstructure, precipitation behavior, and strengthening mechanisms were studied. The results showed that the strengths of quenched steels were higher than those of air-cooled steels, and the increase in strength was more pronounced with the addition of Nb-V than with the addition of Nb alone in the steels. Under the same cooling condition, the strengths of Nb-V-added steels were larger than those of Nb-added steels. Additionally, the Nb-V addition promotes the formation of lath structures. The yield stress of the steels, calculated by using measured microstructural parameters following the linear addition of strengthening, is in good agreement with the measured values.
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