Ageing Effects on Microstructure, Mechanical Properties, and Fracture Behaviour of 9Cr-1.5Mo-1Co-VNbBN Martensitic Steel Welded Joint for High Temperature Application

Falat, Ladislav; Homolová, Viera; Čiripová, Lucia; Ševc, Peter; Svoboda, Milan

doi:10.1155/2017/6824385

Cited by 10 publications

(3 citation statements)

References 24 publications

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“…The knowledge about phase equilibria of the B-Cr-Fe system is important in several fields of materials research. The system is subsystem of various complex alloys, for example, modified ferritic steels for energy industry [1][2][3], steels for production abrasive, and corrosion-resistant components [4]. Information about the system is also important for study of boride coatings on various alloys and metals, including iron [5,6].…”

Section: Introductionmentioning

confidence: 99%

Experimental Investigation of Isothermal Section of the B-Cr-Fe Phase Diagram at 1353 K

Homolová

Čiripová

2017

Advances in Materials Science and Engineering

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The isothermal section of the B-Cr-Fe ternary system was studied experimentally at 1353 K. X-ray diffraction and scanning electron microscopy equipped with EDX analyzer were used for determination of phase equilibria and composition of the coexisting phases in the B-Cr-Fe model alloys after long-term annealing (1500–2205 h). Two iron borides FeB and Fe2B, six chromium borides Cr2B, Cr5B3, CrB, Cr3B4, CrB2, and CrB4 and also iron and chromium solid solutions (α(Fe,Cr), α(Cr,Fe), γ(Fe,Cr)) and β-rhombohedral B were observed in the alloys. High solubilities of the third element in binary borides and no ternary phase were found. Based on the experimental results, isothermal section of the B-Cr-Fe system at 1353 K was determined.

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Section: Introductionmentioning

confidence: 99%

Experimental Investigation of Isothermal Section of the B-Cr-Fe Phase Diagram at 1353 K

Homolová

Čiripová

2017

Advances in Materials Science and Engineering

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“…For welded joints of the steels P91 [3] and P92 [4], creep tests have shown that the fracture of the specimens under high load occurs in the weld metal (Type I) and is shifted into the heat affected zone (HAZ) at lower load and longer test duration (Type IV). Falat et al [5] describe a similar result for TIG welds in CB2 heat-resistant steel. However, such a shift of the fracture location from the weld metal into the HAZ does not always occur.…”

Section: Introductionmentioning

confidence: 56%

Solidification phenomena in creep resistant 9Cr weld metals and their implications on mechanical properties

Nitsche

2020

Weld World

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Martensitic 9% Cr steels play an important role in the implementation of modern and efficiency-enhanced power generation technologies. In the presented study, metallurgical solidification phenomena in heat-resistant 9% Cr filler metals and their effects on the mechanical properties of the weld metal were analysed. The focus was on welded joints of steel grades P91 and CB2, which were welded with flux-cored wires. The investigation of welded joints and weld metals in the creep-damaged and unloaded condition provided detailed inspects into the formation and development of inhomogeneous areas. The microstructure of the individual weld metals was characterized in detail in the as-welded and in the heat-treated condition. It became apparent that inhomogeneities were formed in large areas of the weld metal. In particular, EDX measurements made it possible to explain these solidification phenomena and trace their development within the manufacturing process of the welded joints. It was found that even a slight uneven distribution of chromium and a diffusion of carbon caused extensive negative effects on the development of weld metal microstructures. In addition, the influence of these microstructural inhomogeneities on both the mechanical weld metal properties and the creep rupture strength is discussed. Finally, test welds were performed to optimize the microstructure of the flux-cored wire weld metal and possibilities to avoid microstructural inhomogeneities were derived. The results show that the short-term and long-term properties of the weld metal are affected by the inhomogeneous areas within the weld metal. In summary, it can be assumed that for steel grades P91 and CB2 the safety of plants in high-temperature operation is not endangered. Keywords 9Cr weld metal. Flux-cored wire. White bands. Inhomogeneities. Creep resistant steel. Grade 91. CB2

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“…Few studies reported that the Z phase in the 9CrMoCoB matrix appears after aging for 67,857 h, and the formation of the Z phase consumes V, Nb, leading to a decrease in the strengthening of precipitate (Ref [22][23][24]. The 9CrMoCoB steel was subjected to a steam temperature of 650°C and a steam pressure of 50 to 120 MPa, and their longest service periods were 67,857 h and 82,649 h, respectively.…”

Section: Introductionmentioning

confidence: 99%

Influence of the Evolution of 9CrMoCoB Steel Precipitates on the Microstructure and Mechanical Properties during High-Temperature Aging

Kuang

Cheng

et al. 2021

J. of Materi Eng and Perform

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In this study, the short-term aging was carried out to reveal the evolution of precipitates and mechanical properties of heat resistant 9CrMoCoB steel during the early creep, replacing the conventional creeping. The tempered martensite lath structure (TMLS) and precipitates were observed in the as-aged 9CrMoCoB steel. TMLS in the matrix underwent a transition to the polygonal ferrite after aging only for 300 h. In comparison, the mean diameter of the precipitates increased from 183 to 267 nm after aging at 650 °C for 300 h. Also, the mean diameter of the precipitates increased from 183 to 302 nm at 700 °C. The room-temperature and high-temperature strength of 9CrMoCoB steel decreased after high-temperature aging, which may be mainly due to precipitates coarsening. Many M23C6 phases precipitate in the prior austenite grain boundary (PAGB) and lath boundary. After aging 100 h, TMLS transformed into polygonal ferrite, and the size of the precipitate at the subgrain boundary was about 100 nm, while after 300 h of high-temperature aging, large precipitates appear (400 nm) in the matrix. After 200 h of high-temperature aging, the obvious growth of precipitates on the PAGB and lath boundary weakens the pinning effect on the PAGB and martensite lath boundary and accelerates the transformation of microstructure and mechanical properties.

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Ageing Effects on Microstructure, Mechanical Properties, and Fracture Behaviour of 9Cr-1.5Mo-1Co-VNbBN Martensitic Steel Welded Joint for High Temperature Application

Cited by 10 publications

References 24 publications

Experimental Investigation of Isothermal Section of the B-Cr-Fe Phase Diagram at 1353 K

Experimental Investigation of Isothermal Section of the B-Cr-Fe Phase Diagram at 1353 K

Solidification phenomena in creep resistant 9Cr weld metals and their implications on mechanical properties

Influence of the Evolution of 9CrMoCoB Steel Precipitates on the Microstructure and Mechanical Properties during High-Temperature Aging

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