Effects of Heating and Cooling Rates on Phase Transformations in 10 Wt Pct Ni Steel and Their Application to Gas Tungsten Arc Welding

Barrick, Erin J.; Jain, Divya; DuPont, J. N.; Seidman, David N.

doi:10.1007/s11661-017-4379-0

Cited by 28 publications

(13 citation statements)

References 34 publications

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“…The residual strain present during welding can destabilize the previous austenite and favor martensitic transformation in this region and its surroundings, as suggested by Chen et al [36]. Although the second layer welding thermal cycle had little influence on the microstructure of the PMZ, it had a strong influence on the microstructure of the HAZ of the substrate, changing it from 100% martensite to ferrite with finely dispersed carbides and small islands of reverse austenite (Figure 3f), as indicated by Barrick et al [37] and Payão Filho [38]. As seen in Figure 3f, the concentration of interdendritic precipitates and the average particle size in the first layer of clad II close to the substrate increased during the welding of the second layer.…”

Section: Microstructural Characterizationmentioning

confidence: 67%

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Microstructural and Mechanical Characterization of the Transition Zone of 9%Ni Steel Cladded with Ni-Based Superalloy 625 by GTAW-HW

Farias

Filho

Azevedo

2018

Metals

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9%Ni steel was recently used for the first time in the field of injection unit (IU) for the injection of CO2 into oil wells. Because such steels are operated in H2S medium and are susceptible to sulfide stress cracking, their pipes are cladded with Ni-based superalloy 625 by using gas tungsten arc welding with a hot wire to prevent this phenomenon from occurring. The transition zone of substrate/clad can have high hardness and low toughness, and promote failure of the component during service; therefore, it is very important to know its characteristics. In this work, this transition zone was analyzed through optical and scanning electron microscopy with energy dispersive X-ray spectrometry and electron backscatter diffraction, as well as Vickers microhardness, shear and bend tests. Metallographic analysis identified type I and II boundaries with distinct chemical gradients, MC-type carbides, Laves/γ eutectics, peninsulas macrosegregation, crystallographic texture close to <100> in the clads, residual strain, and drop of microhardness across the transition zone. The clads were approved in the shear and bend tests. This work proposes a new type II boundary formation mechanism in dissimilar welds of steels that do not exhibit the allotropic transformation δ → γ during the welding thermal cycle and do not experience a change in the solidification mode.

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Section: Microstructural Characterizationmentioning

confidence: 67%

“…As already mentioned, after the welding of the 1st L C II, the CGHAZ of 9%Ni steel was composed almost entirely of fresh martensite [37,38]. Nippes and Balaguer [5], when studying joint welding of this steel, observed the presence of a small amount of retained austenite in the CGHAZ.…”

Section: Samplesmentioning

confidence: 98%

Microstructural and Mechanical Characterization of the Transition Zone of 9%Ni Steel Cladded with Ni-Based Superalloy 625 by GTAW-HW

Farias

Filho

Azevedo

2018

Metals

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“…1,45,46) and other low-carbon steels (Refs. [47][48][49]. It should be mentioned that it is different than plate martensite, which occurs for high-carbon steels.…”

Section: Microstructural Evolutionmentioning

confidence: 99%

Effect of Multiple Weld Thermal Cycles on HSLA-100 Steel

2019

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“…The formation of a similar Ni-rich martensite has been reported in other studies. [43][44][45][46] . The martensite morphology is largely effected by the initial microstructure prior to aging.…”

Section: Ni-rich Martensitementioning

confidence: 99%

“…The initiation sites for the parent austenite formation are the martensite laths or prior austenite grain boundaries (PAGB). 43,44,47,48 The austenite that forms at the PAGB and/or lath boundaries will transform to a Ni-rich martensite, and take the form of rod-like morphology or blocky morphology, also described in the literature as "islands". 49 The blocky Ni-rich martensite forms mostly at the PAGB, while the rodlike martensite forms on the martensite laths.…”

Section: Ni-rich Martensitementioning

confidence: 99%

Development of Novel Functionally Graded Transition Joints for Improving the Creep Strength of Dissimilar Metal Welds in Nuclear Applications

DuPont

Babu

Zhao

2018

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Steam generators of the small modular Very High Temperature Reactor (VHTR) will require use of Alloy 800 and 2.25Cr-1Mo steel in different regions depending on temperature and corrosion resistance requirements. As a result, Dissimilar Metal Welds (DMWs) between these two materials are critical for design, development, and manufacturing of the VHTR. DMWs are also used in many other applications in the power generation and petrochemical industries. Experience has demonstrated that failures of such DMWs can occur prematurely well below the expected creep life of either base metal, and these failures have significant consequences in terms of plant reliability, safety, and economic impact. These DMWs failures are caused by the abrupt change in composition that occurs at the weld interface between the two alloys. In this research, the concept of developing and optimizing Graded Transition Joints (GTJ) was developed through an integrated modeling and experimental approach. With GTJs, the composition is gradually graded between the two alloys, thus eliminating the sharp change in composition that causes failure. Microstructural modeling was first conducted to identify the optimum grade length required for improved resistance to carbon diffusion that is largely responsible for premature failure. Next, GTJs were fabricated and characterized in detail to understand how the microstructure evolves during fabrication and long term aging. Finally, the creep behavior of the GTJs was investigated and compared to that of conventional DMWs to demonstrate the superior creep strength of the GTJs.

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Effects of Heating and Cooling Rates on Phase Transformations in 10 Wt Pct Ni Steel and Their Application to Gas Tungsten Arc Welding

Cited by 28 publications

References 34 publications

Microstructural and Mechanical Characterization of the Transition Zone of 9%Ni Steel Cladded with Ni-Based Superalloy 625 by GTAW-HW

Microstructural and Mechanical Characterization of the Transition Zone of 9%Ni Steel Cladded with Ni-Based Superalloy 625 by GTAW-HW

Effect of Multiple Weld Thermal Cycles on HSLA-100 Steel

Development of Novel Functionally Graded Transition Joints for Improving the Creep Strength of Dissimilar Metal Welds in Nuclear Applications

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