Identification of microstructural zones and thermal cycles in a weldment of modified 9Cr-1Mo steel

Paul, V. Thomas; Saroja, S.; Hariharan, P.; Rajadurai, A.; Vijayalakshmi, M.

doi:10.1007/s10853-006-0704-5

Cited by 34 publications

(37 citation statements)

References 16 publications

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“…[32] In the present study, computation of the phase evolution took into consideration the difference in composition between the RAFM steels and the thermal cycle undergone by different regions of the weldment during TIG welding. [22] Equilibrium phases were identified by thermodynamic calculations using Gibb's energy minimization routines proposed by Kattner et al [33] and Lukas et al [34] III. RESULTS AND DISCUSSION…”

Section: Methodsmentioning

confidence: 99%

“…[20] However, in fusion welding, the weldment would possess a highly heterogeneous microstructure depending on the distance of a region from the heat source and number of passes employed. [21,22] Since it is the microstructure that decides the response of a weldment to stresses subsequent to post-weld heat treatment or during long-term service exposures [23,24] many experimental studies focused on the change in structure and property of weld and HAZ upon varying the heat input and cooling rates during welding. [25,26] Recently, genetic algorithm-based computation was attempted for optimizing the chemistry of RAFM steels in order to achieve desired volume fraction and coarsening rate of M 23 C 6 carbides and Laves phase.…”

Section: Introductionmentioning

confidence: 99%

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Influence of Alloy Content and Prior Microstructure on Evolution of Secondary Phases in Weldments of 9Cr-Reduced Activation Ferritic-Martensitic Steel

Paul

Sudha

Saroja

2015

Metall Mater Trans A

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9Cr-Reduced Activation Ferritic-Martensitic steels with 1 and 1.4 wt pct tungsten are materials of choice for the test blanket module in fusion reactors. The steels possess a tempered martensite microstructure with a decoration of inter-and intra-lath carbides, which undergoes extensive modification on application of heat. The change in substructure and precipitation behavior on welding and subsequent thermal exposure has been studied using both experimental and computational techniques. Changes i.e., formation of various phases, their volume fraction, size, and morphology in different regions of the weldment due to prolonged thermal exposure was influenced not only by the time and temperature of exposure but also the prior microstructure. Laves phase of type Fe 2 W was formed in the high tungsten steel, on aging the weldment at 823 K (550°C). It formed in the fine-grained heat-affected zone (HAZ) at much shorter durations than in the base metal. The accelerated kinetics has been understood in terms of enhanced precipitation of carbides at lath/grain boundaries during aging and the concomitant depletion of carbon and chromium and enrichment of tungsten in the vicinity of the carbides. Therefore, the fine-grained HAZ in the weldment was identified as a region susceptible for failure during service.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Influence of Alloy Content and Prior Microstructure on Evolution of Secondary Phases in Weldments of 9Cr-Reduced Activation Ferritic-Martensitic Steel

Paul

Sudha

Saroja

2015

Metall Mater Trans A

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“…Figure 8 shows micrographs produced by scanning electron microscopy and transmission electron microscopy of a normalised and tempered P(T)91 steel. 40 Figure 8a shows a scanning electron microscopy (SEM) image of prior austenite grain boundaries (PAGBs), and higher magnification reveals well defined laths of tempered martensite structure with the carbide precipitates visible. During long creep exposure (thousands of hours at 600uC), the tempered martensitic structure changes by precipitation of a Laves phase Fe 2 (W, Mo) and a Z phase that is a complex nitride of the type Cr (Nb, V) N. The concentration of W and Mo in the alloy determines the amount of Laves phase that forms.…”

Section: Candidate Ferritic Alloys For Ausc Boilersmentioning

confidence: 99%

Welding and weldability of candidate ferritic alloys for future advanced ultrasupercritical fossil power plants

David¹,

Siefert²,

Feng³

2013

Science and Technology of Welding and Joining

102

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Fossil fuels continue to be the primary source of energy in the world. The worldwide demand for clean and affordable energy will continue to grow, and a strong emphasis has been placed on increasing the efficiency and reducing the carbon footprint of new and existing fossil fired power plants. Throughout Asia, Europe and the USA, this demand is being met with programmes to develop advanced materials that have enhanced high temperature creep and corrosion properties. A new class of ferritic alloys, known as creep strength enhanced ferritic steels, has been developed to meet these requirements. This article focuses on the weldability of the advanced ferritic alloys used in boilers and boiler components of ultrasupercritical coal fired power plants. This review focuses on alloy selection; welding and weldability issues, including in service weld failure such as type IV cracking; welding of dissimilar metals; and weld repair. Future articles will address the welding and weldability issues of two other classes of materials, namely austenitic stainless steels and nickel base superalloys.

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“…Los bloques encontrados en la probeta PMoW fueron de menor tamaño y asociados a la línea de fusión. La presencia de ferrita delta en zonas cercanas a la línea de fusión también ha sido observada por otros autores [10]. Una velocidad de enfriamiento elevada en esta zona retiene la ferrita generada a altas temperaturas sin transformar.…”

Section: Estudios De La Junta Soldadaunclassified

Caracterización de soldaduras circunferenciales de aceros avanzados 9Cr: parte 1

et al. 2014

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ResumoOs aços 9%Cr são amplamente utilizados à alta temperatura, principalmente em aplicações relacionadas à geração de energia. Ultimamente têm sido desenvolvidas variantes desses materiais incorporando B, W e Co, entre outros elementos, ao sistema de liga. Devido à escassez de informação sobre a influência do procedimento de soldagem sobre a junta soldada, neste trabalho se estudou o comportamento do metal base e do metal de solda em juntas circunferências soldadas com dois consumíveis diferentes pelo processo de soldagem semi-automático FCAW, sob proteção gasosa de Ar/20%CO 2 . Realizaram-se tratamentos térmicos pós-soldagem a 760°C durante 4 e 2 horas. Utilizaram-se dois arames tubulares de escória rutílica, ligados ao 9Cr1Mo e 9Cr0,5Mo1WCo. Analisou-se a microestrutura nas zonas do metal de solda, afetada pelo calor (zonas de grão grosso, grão fino, intercrítica e subcrítica) e metal base. Determinaram-se a composição química do metal de solda e as propriedades de tração transversal da junta, e realizaram levantamento do perfil de microdureza. Em todos os casos se observaram valores máximos de dureza na zona correspondente ao metal de soldadura e uma diminuição na zona afetada pelo calor desde a zona de grão grosso até o metal base, obtendo se valores mínimos na zona intercrítica, inferiores aos correspondentes ao aço base. Tanto a dureza como a resistência à tração aumentaram quando foi utilizado o arame 9Cr0,5Mo1W. O tratamento térmico mais curto permitiu alcançar maior resistência em todos os casos. Numa próxima etapa se fará as medições de tenacidade e de resistência ao creep. Palavras-chave: Aço 9Cr; Tratamento térmico pós-soldagem; Microestrutura; Junta soldada; Arames tubulares.Abstract: 9Cr steels are widely used for high temperature service, principally in applications related to energy generation. Lately several variants of these materials have been developed through the addition of B, W and Co, among others. Due to the fact that information on influence of welding procedure on the welded joint is scarce, the objective of this work was to study the behavior of both the base metal and the weld metal of circumferential weldments performed using semiautomatic welding process under gas mixture protection. Two FCAW rutilic slag wires, alloyed with 9Cr1Mo and 9Cr0.5Mo1W1Co respectively, were used under Ar/20%CO 2 gas shielding. Post weld heat treatments of 4 and 2 hours have been carried out. The microstructure was analyzed in the different zones: weld metal, heat affected (coarse and fine grain, intercritical and subcritical) and not affected base metal. Chemical composition of the weld metal, transversal tensile properties of the joint and microhardness along the weld transversal section were determined. In all cases it was obtained maximum hardness values in the weld metal and a decrease in this property in the heat affected zone from the coarse grain zone to the base metal one. The minimal hardness values were achieved in the intercritical zone, lower than those of the metal base. Hardness and tensi...

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Identification of microstructural zones and thermal cycles in a weldment of modified 9Cr-1Mo steel

Cited by 34 publications

References 16 publications

Influence of Alloy Content and Prior Microstructure on Evolution of Secondary Phases in Weldments of 9Cr-Reduced Activation Ferritic-Martensitic Steel

Influence of Alloy Content and Prior Microstructure on Evolution of Secondary Phases in Weldments of 9Cr-Reduced Activation Ferritic-Martensitic Steel

Welding and weldability of candidate ferritic alloys for future advanced ultrasupercritical fossil power plants

Caracterización de soldaduras circunferenciales de aceros avanzados 9Cr: parte 1

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