Creep Resistance of VM12 Steel

Zieliński, A.; Golański, G.; Dobrzański, J.; Sroka, M.

doi:10.1515/amm-2016-0265

Cited by 24 publications

(32 citation statements)

References 4 publications

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“…The increase in the size of precipitates was found after this time of annealing. The increase in the size of precipitates observed in this paper is also presented in [4,17]. As expected, their size was bigger after long-term annealing at 650ºC (Fig.…”

Section: Mechanical Propertiessupporting

confidence: 88%

“…The highest decrease in their values is observed for the impact energy of the tested steels out of which VM12 showed the highest impact energy loss from 78J for the as-received condition to 29J after annealing at 650°C for 30,000 h. 2. As a result of increasing the time of exposure at elevated temperature, the microstructure of the tested steels is subject to continuous degradation, which manifests itself in the increased amount and size of precipitates at the prior austenite grain boundaries and the martensite lath boundaries [4,5,7,17]. As expected, the highest microstructure degradation was observed for the tested steels after 30,000 h annealing at 650°C (Fig.…”

Section: Discussionsupporting

confidence: 54%

“…The basic requirements placed on all creep-resisting steels are that they should maintain, for a long time, the assumed mechanical properties, high-temperature creep resistance and heat resistance as the elements of safe (reliable) operation within the design working parameters of boiler [1][2][3][4][5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Changes In Properties and Microstructure of High-Chromium 9-12%Cr Steels Due to Long-Term Exposure at Elevated Temperature

Zieliński

Dobrzański

Purzyńska

et al. 2016

Archives of Metallurgy and Materials

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This paper presents the characteristics of the performance of P91 (X10CrMoVNb9-1), P92 (X10CrWMoVNb9-2) and VM12 (X12CrCoWVNb12-2-2) steels used for condition assessment of the pressure components of boilers with supercritical steam parameters. Studies on the mechanical properties, microstructure tests using scanning and transmission electron microscopy, and X-ray analysis of the phase composition of precipitates were performed for selected steels in the as-received condition and after long-term annealing. These steel characteristics are used for the evaluation of the microstructural changes and mechanical properties of the material of components after long-term service. The result of this study is the database of material characteristics representing the mechanical properties related to the microstructure analysis and it can be used for diagnosis of the components of pressure parts of power boilers.Keywords: steel P91, P92, VM12, microstructure, mechanical properties, long-term annealing inspections, and possible repairs are carried out during the boiler's lifetime to ensure safe and failure-free operation of power units. In safety assessment of the pressure equipment in which new creep-resisting steels were used, it is essential that a number of tests should be carried out to allow the evaluation of their condition and suitability for further operation beyond the design work time under further operation conditions [7,8,[12][13][14][15][16][17][18][19].In cooperation with other research centres (Silesian University of Technology, Czestochowa University of Technology, AGH University of Science and Technology in Cracow) as well as the boiler factories Rafako S.A. and SEFKAO S.A. -the leading manufacturers of boilers, the Institute for Ferrous Metallurgy performs the works on the advance and verification testing of new-generation steels for the power industry [2,7,8,19,21,23].This study presents the results of investigations on the mechanical properties in the as-received condition as well as the effect of long-term impact of elevated temperature and stress on the change in properties of 9-12%Cr steel. Test sampleThe test sample was P91 (X10CrMoVNb9-1), P92 (X10Cr-WMoVNb9-2) and VM12 (X12CrCoWVNb12-2-2) steels in the as-received condition after heat treatment and after long-term exposure at elevated temperature. The chemical composition of the examined steels is summarised in Table 1.

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Section: Mechanical Propertiessupporting

confidence: 88%

Section: Discussionsupporting

confidence: 54%

See 1 more Smart Citation

Changes In Properties and Microstructure of High-Chromium 9-12%Cr Steels Due to Long-Term Exposure at Elevated Temperature

Zieliński

Dobrzański

Purzyńska

et al. 2016

Archives of Metallurgy and Materials

Self Cite

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“…Assessment of the reliability (safety) of the elements of pressure devices made of creep-resistant steels is carried out on the basis of the data obtained as a result of many tests. These are performed not only for the materials in the as-received condition but also after service, in various states of degradation of the microstructure and functional properties (Ref 11,12).…”

Section: Introductionmentioning

confidence: 99%

Effect of Long-Term Service on Microstructure and Mechanical Properties of Martensitic 9% Cr Steel

Golański

Zielińska‐Lipiec²,

Zieliński

et al. 2017

J. of Materi Eng and Perform

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The paper presents the results of research on the X10CrMoVNbN9-1 (T91) steel after long-term service. The material for testing was taken from a pipe section of a boiler superheater coil serviced for around 105,000 h at the temperature of 540°C, at the pressure of 12.5 MPa. A quantitative analysis including the measurement of mean diameter of subgrains and precipitates as well as the density of dislocations of the examined steel was performed by means of TEM. The microscopic tests of T91 steel were complemented with the results of tests on mechanical properties which included also the short creep tests. After service, the investigated steel was characterized by a retained lath microstructure of tempered martensite with fine subgrain and quite large density of dislocations as well as numerous precipitates. In the microstructure, apart from the particles of M 23 C 6 and MX (VX, NbC, V-wings), the precipitates of Laves phase and single particles of Z phase were revealed. It has been shown that the extent of degradation of the T91 steel microstructure was minor, which resulted from its low temperature of service. Performed tests of mechanical properties showed that these properties fulfilled the minimum requirements for this steel in the as-received condition. A favorable influence of fine precipitates of Laves phase on mechanical properties was observed. Moreover, an insignificant influence of single precipitates of Z phase on the creep resistance of the examined steel was stated.

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“…the exhaustion degree, based on changes in the microstructure of the analysed material, the examinations should be made by scanning electron microscopy with magnifications of up to 5 000x and suitable resolution of microstructure images. The evaluation of exhaustion degree of the examined materials based on nondestructive testing requires a database including the material characteristics of changes in the level of mechanical properties and residual creep strength with regard to the condition of microstructure [15][16][17][18]. It concerns not only the diagnostics of welded joints after long-term service, but above all the assessment of behaviour of the material and repair welded joints in the as-received condition with material after longterm service [19][20][21][22][23].…”

Section: Introductionmentioning

confidence: 99%

The Service Life of the Repair Welded Joint of Cr-Mo / Cr-Mo-V

Sroka¹,

Zieliński²,

Mikuła³

2016

Archives of Metallurgy and Materials

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This paper presents the evaluation of the service life of dissimilar repair welded joint from Cr-Mo/Cr-Mo-V steel after 200,000 h service under creep condition. The investigations of microstructure using scanning electron microscopy, investigations of mechanical properties at room and elevated temperature as well as creep tests of the basic material from Cr-Mo and Cr-Mo-V steel and welded joint from these steels were carried out. The investigations allowed the time of further safe operation of the repair welded joint in relation to the residual life of the materials to be determined. The evaluation of residual life and disposable residual life, and thus the estimation or determination of possible time of further safe operation, is crucial when the elements are operated much beyond the design work time.

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Creep Resistance of VM12 Steel

Cited by 24 publications

References 4 publications

Changes In Properties and Microstructure of High-Chromium 9-12%Cr Steels Due to Long-Term Exposure at Elevated Temperature

Changes In Properties and Microstructure of High-Chromium 9-12%Cr Steels Due to Long-Term Exposure at Elevated Temperature

Effect of Long-Term Service on Microstructure and Mechanical Properties of Martensitic 9% Cr Steel

The Service Life of the Repair Welded Joint of Cr-Mo / Cr-Mo-V

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