Coarsening of nano sized carbide particles in 2.25Cr–1Mo power plant steel after extended service

Jayan, V.; Khan, Muhammad Yasir; Husain, Muhammad

doi:10.1016/j.matlet.2004.02.051

Cited by 16 publications

(5 citation statements)

References 16 publications

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“…These observations clearly suggest that coarsening of precipitates take place as a result of increase in the severity of ageing treatment. Present results on sequence of precipitation and coarsening of precipitates are found to be consistent with the reported observation in the literature [7,8].…”

Section: Figuresupporting

confidence: 93%

“…The Mo 2 C forms a high density of fine needles or platelets and thus, contributes to strengthening by dispersion hardening [7]. As the degree of ageing is increased, the unstable Mo 2 C carbides eventually transforms to larger globular particles of various carbides [7,8]. Not only that the amount of precipitates increased as a result of increase in the degree of ageing but the size and shape of carbides also changed with the severity of ageing.…”

Section: Figurementioning

confidence: 99%

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Assessment of Microstructural Degradation in 2.25Cr-1Mo Steel Using Miniature Specimen Technique

Jha

Sahoo

Tripathy

et al. 2011

DDF

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Miniature specimen techniques viz. small-punch tests (SPT) have been carried out at room temperature in order to correlate the microstructural degradation of 2.25Cr-1Mo steel with that of SPT parameters. Microstructural degradation of this steel has been introduced as a result of thermal ageing corresponding to Larson-Miller parameters (LMP) values of 33,012, 35,402, 37,846 and 38,374. SPT parameters viz. total area and area under the region of plastic instability of the load-displacement curve have been found to decrease with an increase in LMP values. A strength parameter viz. UTS obtained using uniaxial tensile tests has also been found to decrease with an increase in LMP values. The results indicated that miniature specimen techniques viz. small-punch test could be successfully used to assess the degradation of microstructures in 2.25Cr-1Mo steel generated due to their exposure to high temperatures.

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Section: Figuresupporting

confidence: 93%

Section: Figurementioning

confidence: 99%

Assessment of Microstructural Degradation in 2.25Cr-1Mo Steel Using Miniature Specimen Technique

Jha

Sahoo

Tripathy

et al. 2011

DDF

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“…Finally, the base metal reached the highest volume fraction of carbide plates compared to that of the HAZ and weld bead, which was associated with the strain induced strengthening during the TMCP process. According to the values listed in Table 2 and aforementioned TEM image analysis, the HAZ and base metal exhibited nano-sized particles and carbide plates with notable coarsening (Jayan et al, 2004, Watanabe et al, 2004 i.e., an increase in their size related to the over-aged condition (Vargas et al, 2006) as a consequence of long periods of time as 21 years. The coarsening process of particles was described by the Ostwald ripening process spoken by Moon et al (2006).…”

Section: Tem Micro-structural Analysismentioning

confidence: 99%

“…A third case is the coarsening study of nano-sized M 23 C 6 carbide precipitate in 2.25Cr-1Mo steel found in boiler tube specimens subjected to extended aging of up to 160,000 hours at 540 °C in a thermal power plant. It is found that the coarsening of these nano-particles reflected in a diffraction pattern as crystallite size increased with aging resulted in material degradation (Jayan et al, 2004). Additionally, a study on the artificial aging of API 5L X52 welded steel carried out at 250 °C for up to 1,000 hour resulted in an increase of the general corrosion rate in a solution of brine containing hydrogen sulphide at 25 °C for the weld bead, HAZ and the base metal as the aging time elapsed.…”

Section: Introductionmentioning

confidence: 99%

Effect of natural aging on the microstructural regions, mechanical properties, corrosion resistance and fracture in welded joints on API5L X52 steel pipeline

et al. 2014

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A characterization study was done to analyze how microstructural regions affect the mechanical properties, corrosion and fractography of the Heat Affected Zone (HAZ), weld bead and base metal for pipe naturally aged for 21 years at 30 °C. Results showed that microstructures exhibited damage and consequently decrease in properties, resulting in over-aged due to service. SEM analysis showed that base metal presented coarse ferrite grain. Tensile test indicated that microstructures showed discontinuous yield. Higher tensile strength was obtained for weld bead, which exhibited a lower impact energy in comparison to that of HAZ and base metal associated with brittle fracture by trans-granular cleavage. The degradation of properties was associated with the coarsening of nano-carbides observed through TEM images analysis, which was confirmed by SEM fractography of tensile and impact fracture surfaces. The weld bead reached the largest void density and highest susceptibility to corrosion in H 2 S media when compared to those of the HAZ and base metal. RESUMEN:Efecto del envejecimiento natural sobre la microestructura, propiedades mecánicas, resistencia a corrosión y fractura en uniones soldadas de acero para tubería API5L X52. Se realizó un estudio de caracterización para analizar cómo la microestructura afecta a las propiedades mecánicas, corrosión y fractura de la zona afectada por calor (ZAC), soldadura y metal base para tubería envejecida naturalmente durante 21 años a 30 °C. Los resultados indicaron que las microestructuras presentaron daño y consecuentemente reducción en propiedades mecánicas, como consecuencia del envejecimiento por servicio. El estudio mediante MEB mostró que el metal base presenta grano ferrítico grueso. La prueba de tensión indicó que las microestructuras mostraron fluencia discontinua. La mayor resistencia a la tracción se presentó en la soldadura, la cual alcanzó menor energía de impacto en comparación con la ZAC y metal base asociado con fractura frágil por clivaje transgranular. La degradación de las propriedades está en relación con el engrosamiento de nanocarburos observados a través del análisis de imágenes por MET, lo que se confirmó mediante fractografía por MEB de superfícies de fractura bajo tensión e impacto. La soldadura alcanzó la mayor densidad de microhuecos y la mayor susceptibilidad a la corrosión en un medio conteniendo H 2 S que cuando se compara con la ZAC y metal base.

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“…It is known that on preferred sites, nucleation of M 23 C 6 occurs in the matrix. Cubic M 23 C 6 is the final equilibrium precipitate phase in this steel with an average crystallite size of~80 nm (specimen G) [20] and hence the quantity of this phase is investigated here in detail. It is known that both M 23 C 6 and M 6 C have similar crystal structure (fcc) with almost same lattice parameter [5] and hence distinguishing them by X-ray diffraction is not possible.…”

Section: Quantitative Analysis Of Equilibrium Carbide Phasementioning

confidence: 99%

X-ray analysis of nano-carbide transformations for actual life assessment of service-exposed 2.25Cr–1Mo boiler tubes in a thermal power station

Jayan¹

2012

Materials at High Temperatures

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Quantification of carbide phase changes by X-ray analysis, with an objective of actual life assessment of service exposed 2.25Cr -1Mo boiler tubes is described. Carbide transformations and their compositional variations in specimens subjected to extended service (~5 -18 years) from a power plant were investigated by X-ray diffraction and X-ray fluorescence analysis of extracted carbide precipitates. Quantitative estimation of equilibrium carbide phase M 23 C 6 by Rietveld's refinement technique showed a systematic increase with service. Carbide composition analysis revealed a decrease in Mo wt% with ageing. Based on this result, two life assessment methods were proposed and applied to few unknown specimens for its validation. The computed life was in good agreement with plant operating data.

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Coarsening of nano sized carbide particles in 2.25Cr–1Mo power plant steel after extended service

Cited by 16 publications

References 16 publications

Assessment of Microstructural Degradation in 2.25Cr-1Mo Steel Using Miniature Specimen Technique

Assessment of Microstructural Degradation in 2.25Cr-1Mo Steel Using Miniature Specimen Technique

Effect of natural aging on the microstructural regions, mechanical properties, corrosion resistance and fracture in welded joints on API5L X52 steel pipeline

X-ray analysis of nano-carbide transformations for actual life assessment of service-exposed 2.25Cr–1Mo boiler tubes in a thermal power station

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