Characterization of complex carbide–silicide precipitates in a Ni–Cr–Mo–Fe–Si alloy modified by welding

Davis, J.; Drew, M.; Harrison, R. P.; Edwards, L.

doi:10.1016/J.MATCHAR.2015.05.001

Title: Characterization of complex carbide–silicide precipitates in a Ni–Cr–Mo–Fe–Si alloy modified by welding

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Abstract

Nickel based alloys of the type Hastelloy-N™ are ideal candidate materials for molten salt reactors, as well as for applications such as pressure vessels, due to their excellent resistance to creep, oxidation and corrosion. In this work, the authors have attempted to understand the effects of welding on the morphology, chemistry and crystal structure of the precipitates in the heat affected zone (HAZ) and the weld zone of a Ni–Cr–Mo–Fe–Si alloy similar to Hastelloy-N™ in composition, by using characterization techniques such as scanning and transmission electron microscopy. Two plates of a Ni–Cr–Mo–Fe–Si alloy GH-3535 were welded together using a TiG welding process without filler material to achieve a joint with a curved molten zone with dendritic structure. It is evident that the primary precipitates have melted in the HAZ and re-solidified in a eutectic-like morphology, with a chemistry and crystal structure only slightly different from the pre-existing precipitates, while the surrounding matrix grains remained unmelted, except for the zones immediately adjacent to the precipitates. In the molten zone, the primary precipitates were fully melted and dissolved in the matrix, and there was enrichment of Mo and Si in the dendrite boundaries after solidification, and re-precipitation of the complex carbides/silicides atmore »« less

Authors:: Davis, J.; Drew, M.; Harrison, R. P.; Edwards, L.

Publication Date:: Wed Jul 15 00:00:00 EDT 2015

OSTI Identifier:: 22476117

Resource Type:: Journal Article

Journal Name:: Materials Characterization

Additional Journal Information:: Journal Volume: 105; Other Information: Copyright (c) 2015 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 1044-5803

Country of Publication:: United States

Language:: English

Subject:: 36 MATERIALS SCIENCE; ALLOY SYSTEMS; BACKSCATTERING; CARBIDES; CHROMIUM COMPOUNDS; CORROSION; CRYSTAL STRUCTURE; ELECTRON DIFFRACTION; EUTECTICS; GRAIN BOUNDARIES; HASTELLOY N; IRON COMPOUNDS; MOLYBDENUM COMPOUNDS; NICKEL COMPOUNDS; PRECIPITATION; SCANNING ELECTRON MICROSCOPY; SILICIDES; SILICON ALLOYS; SPECTROSCOPY; TRANSMISSION ELECTRON MICROSCOPY; WELDED JOINTS

Citation Formats


                    Bhattacharyya, D., E-mail: dhb@ansto.gov.au, Davis, J., Drew, M., Harrison, R. P., and Edwards, L. Characterization of complex carbide–silicide precipitates in a Ni–Cr–Mo–Fe–Si alloy modified by welding.  United States: N. p., 2015. 
        Web.  doi:10.1016/J.MATCHAR.2015.05.001.

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                    Bhattacharyya, D., E-mail: dhb@ansto.gov.au, Davis, J., Drew, M., Harrison, R. P., & Edwards, L. Characterization of complex carbide–silicide precipitates in a Ni–Cr–Mo–Fe–Si alloy modified by welding.  United States.  https://doi.org/10.1016/J.MATCHAR.2015.05.001

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                    Bhattacharyya, D., E-mail: dhb@ansto.gov.au, Davis, J., Drew, M., Harrison, R. P., and Edwards, L. 2015.  
        "Characterization of complex carbide–silicide precipitates in a Ni–Cr–Mo–Fe–Si alloy modified by welding".  United States.  https://doi.org/10.1016/J.MATCHAR.2015.05.001.

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@article{osti_22476117,

  title        = {Characterization of complex carbide–silicide precipitates in a Ni–Cr–Mo–Fe–Si alloy modified by welding},

  author       = {Bhattacharyya, D., E-mail: dhb@ansto.gov.au and Davis, J. and Drew, M. and Harrison, R. P. and Edwards, L.},

  abstractNote = {Nickel based alloys of the type Hastelloy-N™ are ideal candidate materials for molten salt reactors, as well as for applications such as pressure vessels, due to their excellent resistance to creep, oxidation and corrosion. In this work, the authors have attempted to understand the effects of welding on the morphology, chemistry and crystal structure of the precipitates in the heat affected zone (HAZ) and the weld zone of a Ni–Cr–Mo–Fe–Si alloy similar to Hastelloy-N™ in composition, by using characterization techniques such as scanning and transmission electron microscopy. Two plates of a Ni–Cr–Mo–Fe–Si alloy GH-3535 were welded together using a TiG welding process without filler material to achieve a joint with a curved molten zone with dendritic structure. It is evident that the primary precipitates have melted in the HAZ and re-solidified in a eutectic-like morphology, with a chemistry and crystal structure only slightly different from the pre-existing precipitates, while the surrounding matrix grains remained unmelted, except for the zones immediately adjacent to the precipitates. In the molten zone, the primary precipitates were fully melted and dissolved in the matrix, and there was enrichment of Mo and Si in the dendrite boundaries after solidification, and re-precipitation of the complex carbides/silicides at some grain boundaries and triple points. The nature of the precipitates in the molten zone varied according to the local chemical composition. - Graphical abstract: Display Omitted - Highlights: • Ni-based alloy with Cr, Mo, Si, Fe and C was welded, examined with SEM, EBSD, and TEM. • Original Ni{sub 2}(Mo,Cr){sub 4}(Si,C) carbides changed from equiaxed to lamellar shape in HAZ. • Composition and crystal structure remained almost unchanged in HAZ. • Original carbides changed to lamellar Ni{sub 3}(Mo,Cr){sub 3}(Si,C) in some cases in weld metal. • Precipitates were mostly incoherent, but semi-coherent in some cases in weld metal.},

  doi          = {10.1016/J.MATCHAR.2015.05.001},

  url          = {https://www.osti.gov/biblio/22476117},
  journal      = {Materials Characterization},

  issn         = {1044-5803},

  number       = ,

  volume       = 105,

  place        = {United States},

  year         = {Wed Jul 15 00:00:00 EDT 2015},

  month        = {Wed Jul 15 00:00:00 EDT 2015}

}

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