Material Characterization of the Main Steam Gate Valve Made of X20CrMoV 12.1 Steel after Long Term Service

Bakić, Gordana; Zeravcic, Vera Sijacki; Djukic, Milos B.; Perunicic, V.; Prodanovic, A.; Rajičić, Bratislav; Gajic, I.; Sekeljic, P.; Gregorjev, N.

doi:10.1016/j.mspro.2014.06.244

Cited by 7 publications

(9 citation statements)

References 6 publications

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“…Within the power industry, the tempered martensitic ferritic 12% Cr steel, known as X20CrMoV12-1 (X20 hereafter) under DIN designation, is well-known. Being considered a vintage alloy in the 9%–12% Cr steel group, X20 has been in service as main steam piping in coal-fired power plants for over 60 years [1]. However, there is continued interest in this steel, as it is currently in use in about half of the power stations in South Africa and, in some cases, has outperformed its replacement P91 (X10CrMoVNb9-1) in terms of damage accumulation [2].…”

Section: Introductionmentioning

confidence: 99%

Creep Damage Assessment of Ex-Service 12% Cr Power Plant Steel Using Digital Image Correlation and Quantitative Microstructural Evaluation

et al. 2019

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The lifetime of steam pipelines in long-term operation in coal-fired power plants are limited due to material damage that resulted from creep exposure. In the present study, the authors comparatively assess the damage of ex-service 12% Cr piping steel with varying degrees of exposure while using accelerated creep tests that employ digital image correlation (DIC) as well as microstructural investigation that is based on electron microscopy. The DIC technique, which allows multiple creep curves to be measured at temperatures ranging from 550–600 °C from a single specimen, revealed higher Zener–Hollomon parameters for a high damage material with a high void density when compared to a material with lower damage and lower void density. Both of the material states showed similar hardness values, subgrain sizes, and boundary character, despite the difference in void densities. Slightly higher inter-particle spacing of MX precipitates results in a lower threshold stress of 79 MPa for the high damage steel when compared to 97 MPa for the low damage material. Besides large Laves phase particles (>0.2 µm) that are found in the higher damaged materials that result in solid solution depletion, the most prominent microstructural damage indicator was a lower density of M23C6 precipitates. Therefore, the observations indicate that the Zener–Hollomon parameter and M23C6 particles are good damage assessment indicators between the most extreme damage states and they predict a lower damage level for a medium void density material.

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Section: Introductionmentioning

confidence: 99%

Creep Damage Assessment of Ex-Service 12% Cr Power Plant Steel Using Digital Image Correlation and Quantitative Microstructural Evaluation

et al. 2019

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“…A ROI of 10 × 5 ( x × y ) mm 2 centred on the gauge area was selected for strain calculation to remain within the uniaxial stress region as established above. Self-correlated tests (correlation of images at no load) at the maximum temperature of 600°C using a subset size of 61 pixels 2 and 15 pixel step size indicate that spatial and temporal strain baseline noises are similar (Table 4) as computed according to iDIC guidelines. 26 By setting the reference DIC image to coincide with when the maximum constant load is reached, only creep strain was included while elastic, plastic and thermal components were excluded.…”

Section: Experimental Methodologymentioning

confidence: 98%

“…27 Grain-size analysis was conducted using the MTEX 5.2 MATLAB R2019a toolbox 29 using a half quadtratic optimization filter with a 1.3° boundary preservation. Grains smaller than 3 pixels 2 were excluded.…”

Section: Experimental Methodologymentioning

confidence: 99%

“…9 Furthermore, replica preparation methods, the presence of inclusions as well as coalescence of cavities nearing the end of the component life result in apparent voids which lead to incorrect damage assessments. 10 When it is practical to remove sufficient material, post-exposure mechanical tests are conducted for damage evaluation of X20 steel, including hardness measurements, 4,11 room temperature tensile tests, 2 impact toughness tests, 2,12 high-temperature tensile tests 5,11 and creep rupture tests. 13 Although hardness measurements are quasi non-destructive and can be applied to small amounts of material, Hu et al 13 found that hardness was not sensitive to the damage state of ex-service X20.…”

Section: Introductionmentioning

confidence: 99%

“…In South Africa, the 12% Cr tempered ferritic-martensitic steel with the DIN designation X20CrMoV12-1 (X20 hereafter) has been the workhorse material for the construction of thick steam pipelines in coal-fired power stations for over half a century. 2 Several researchers have investigated the creep strength, 3 microstructural properties, 4 deformation behaviour 4,5 and damage formation 6 of X20. Although the understanding of X20 laboratory-generated properties is well established, there is still a need for research into the response of ‘ex-service’ power plant X20 to damage assessment techniques for life monitoring.…”

Section: Introductionmentioning

confidence: 99%

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Measurement of creep deformation of ex-service 12% Cr steel using digital image correlation

Rooyen

Becker

Westraadt

et al. 2020

The Journal of Strain Analysis for Engineering Design

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The effective operation of ageing coal-fired power plants requires routine damage assessment of critical component materials throughout their service history. Traditional post-exposure mechanical testing typically requires large amounts of material for each testing condition. This study introduces an accelerated (high stress and temperature) creep testing technique that employs digital image correlation for strain measurement over a non-uniform temperature field generated by a thermomechanical tester. When applied to different ex-service (exposed to service conditions within a power plant) 12% Cr piping steels, multiple accelerated creep curves at temperatures ranging from 550°C to 600°C are measured from a single specimen for each material condition. Higher creep damage in the steel due to longer service exposure and higher void densities is revealed by shorter rupture times, faster creep rates and tertiary-dominated creep curves when compared to the lower creep damage state. Microstructural study via quantitative electron microscopy confirms the dislocation creep-driven growth of subgrains in the specimen gauge regions relative to the grips. Larger subgrains and a weakening of precipitate distributions for the high damage material were also noted. Digital image correlation–measured strains are in good agreement with traditional techniques of creep testing with standard extensometry. On a comparative basis, the technique is shown to be a plausible form of damage assessment of 12% Cr piping steels with varying levels of service exposure and serve as a suitable mechanical complement to the traditional void replica methodology.

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Characterization of Tube Repair Weld in Thermal Power Plant Made of a 12%Cr Tempered Martensite Ferritic Steel

Bakić

Djukic

Rajičić

et al. 2016

Fracture at All Scales

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Material Characterization of the Main Steam Gate Valve Made of X20CrMoV 12.1 Steel after Long Term Service

Cited by 7 publications

References 6 publications

Creep Damage Assessment of Ex-Service 12% Cr Power Plant Steel Using Digital Image Correlation and Quantitative Microstructural Evaluation

Creep Damage Assessment of Ex-Service 12% Cr Power Plant Steel Using Digital Image Correlation and Quantitative Microstructural Evaluation

Measurement of creep deformation of ex-service 12% Cr steel using digital image correlation

Characterization of Tube Repair Weld in Thermal Power Plant Made of a 12%Cr Tempered Martensite Ferritic Steel

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