Microstructural and Mechanical Characterization of the Transition Zone of 9%Ni Steel Cladded with Ni-Based Superalloy 625 by GTAW-HW
9%Ni steel was recently used for the first time in the field of injection unit (IU) for the injection of CO<sub>2</sub> into oil wells. Because such steels are operated in H<sub>2</sub>S medium and are susceptible to sulfide stress cracking, their pipes are cladded with Ni-ba...
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| Format: | Article |
| Language: | English |
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MDPI AG
2018-12-01
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| Series: | Metals |
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| Online Access: | https://www.mdpi.com/2075-4701/8/12/1007 |
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| author | Francisco Werley Cipriano Farias João da Cruz Payão Filho Luiz Maurício Barreto de Azevedo |
| author_facet | Francisco Werley Cipriano Farias João da Cruz Payão Filho Luiz Maurício Barreto de Azevedo |
| author_sort | Francisco Werley Cipriano Farias |
| collection | DOAJ |
| description | 9%Ni steel was recently used for the first time in the field of injection unit (IU) for the injection of CO<sub>2</sub> into oil wells. Because such steels are operated in H<sub>2</sub>S 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/<i>γ</i> 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 <i>δ</i> → <i>γ</i> during the welding thermal cycle and do not experience a change in the solidification mode. |
| first_indexed | 2024-12-10T10:44:26Z |
| format | Article |
| id | doaj.art-39032ffceb474dccb30d77101fde585c |
| institution | Directory Open Access Journal |
| issn | 2075-4701 |
| language | English |
| last_indexed | 2024-12-10T10:44:26Z |
| publishDate | 2018-12-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Metals |
| spelling | doaj.art-39032ffceb474dccb30d77101fde585c2022-12-22T01:52:12ZengMDPI AGMetals2075-47012018-12-01812100710.3390/met8121007met8121007Microstructural and Mechanical Characterization of the Transition Zone of 9%Ni Steel Cladded with Ni-Based Superalloy 625 by GTAW-HWFrancisco Werley Cipriano Farias0João da Cruz Payão Filho1Luiz Maurício Barreto de Azevedo2Department of Metallurgical and Materials Engineering, Universidade Federal do Rio de Janeiro COPPE/UFRJ, Cx. Postal 68505, CEP 21941-972, Rio de Janeiro, RJ, BrazilDepartment of Metallurgical and Materials Engineering, Universidade Federal do Rio de Janeiro COPPE/UFRJ, Cx. Postal 68505, CEP 21941-972, Rio de Janeiro, RJ, BrazilDepartment of Metallurgical and Materials Engineering, Universidade Federal do Rio de Janeiro COPPE/UFRJ, Cx. Postal 68505, CEP 21941-972, Rio de Janeiro, RJ, Brazil9%Ni steel was recently used for the first time in the field of injection unit (IU) for the injection of CO<sub>2</sub> into oil wells. Because such steels are operated in H<sub>2</sub>S 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/<i>γ</i> 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 <i>δ</i> → <i>γ</i> during the welding thermal cycle and do not experience a change in the solidification mode.https://www.mdpi.com/2075-4701/8/12/1007weldmentscladdingweld overlaydissimilar transition zoneinterface of dissimilar metalstype II boundaryelectron backscatter diffraction (EBSD)cryogenic steelcorrosion resistant alloyCO<sub>2</sub> injection unit |
| spellingShingle | Francisco Werley Cipriano Farias João da Cruz Payão Filho Luiz Maurício Barreto de Azevedo Microstructural and Mechanical Characterization of the Transition Zone of 9%Ni Steel Cladded with Ni-Based Superalloy 625 by GTAW-HW Metals weldments cladding weld overlay dissimilar transition zone interface of dissimilar metals type II boundary electron backscatter diffraction (EBSD) cryogenic steel corrosion resistant alloy CO<sub>2</sub> injection unit |
| title | Microstructural and Mechanical Characterization of the Transition Zone of 9%Ni Steel Cladded with Ni-Based Superalloy 625 by GTAW-HW |
| title_full | Microstructural and Mechanical Characterization of the Transition Zone of 9%Ni Steel Cladded with Ni-Based Superalloy 625 by GTAW-HW |
| title_fullStr | Microstructural and Mechanical Characterization of the Transition Zone of 9%Ni Steel Cladded with Ni-Based Superalloy 625 by GTAW-HW |
| title_full_unstemmed | Microstructural and Mechanical Characterization of the Transition Zone of 9%Ni Steel Cladded with Ni-Based Superalloy 625 by GTAW-HW |
| title_short | Microstructural and Mechanical Characterization of the Transition Zone of 9%Ni Steel Cladded with Ni-Based Superalloy 625 by GTAW-HW |
| title_sort | microstructural and mechanical characterization of the transition zone of 9 ni steel cladded with ni based superalloy 625 by gtaw hw |
| topic | weldments cladding weld overlay dissimilar transition zone interface of dissimilar metals type II boundary electron backscatter diffraction (EBSD) cryogenic steel corrosion resistant alloy CO<sub>2</sub> injection unit |
| url | https://www.mdpi.com/2075-4701/8/12/1007 |
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