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Eutectic Backfilling: A Fundamental Investigation into Compositional Effects on the Nature of this Crack Healing Phenomenon for Ni-30Cr Weld Applications

Wheeling, Rebecca Ann

Abstract Details

2018, Doctor of Philosophy, Ohio State University, Welding Engineering.
This research seeks to understand eutectic backfilling and its utilization as a technique to combat solidification cracking in Ni-30Cr weld metal as function of Nb and Mo content. Initial research has suggested that levels of Nb greater than 4 wt.% in alloy 690 may increase the volume fraction eutectic enough to reduce solidification cracking susceptibility via a eutectic backfilling or crack healing mechanism. Mo additions appear to produce no substantial change in fraction eutectic but still result in a significant decrease in cracking susceptibility in some instances. Since Mo additions don’t remarkably change the fraction eutectic, it is possible that the Mo may increase the “wettability” of this eutectic liquid, relative to the Nb-rich eutectic, with respect to grain boundaries, allowing it to backfill more quickly or efficiently. A reduction in cracking susceptibility would thereby result from the ability of a eutectic liquid to more completely backfill and heal cracks. Gleeble reheat tests produced qualitative confirmation that eutectic wettability at grain boundaries changed between the Nb- and NbMo- bearing alloys. Weldability test variations of the varestraint and strain-to-fracture tests have provided quantitative evidence of varied grain boundary wettability among varied eutectic compositions. Additional investigations suggest that interstitial nitrogen additions play a role in backfilling and that grain boundary orientations may produce slight preferences regarding boundaries that exhibit backfilling relative to those that do not. The objective of this study is to explore backfilling tendencies as a function of composition, specifically concentrating on the grain boundary wettability aspect. Gaining a fundamental understanding of the effect of Mo on grain boundary wetting of the Nb-rich eutectic liquid will impact a number of industries that rely on Ni-base filler metals, including power generation and petrochemical. Applying these principles to new material and eutectic systems could widen the industrial application scope.
John Lippold (Advisor)
271 p.

Recommended Citations

Citations

  • Wheeling, R. A. (2018). Eutectic Backfilling: A Fundamental Investigation into Compositional Effects on the Nature of this Crack Healing Phenomenon for Ni-30Cr Weld Applications [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1523349907312233

    APA Style (7th edition)

  • Wheeling, Rebecca. Eutectic Backfilling: A Fundamental Investigation into Compositional Effects on the Nature of this Crack Healing Phenomenon for Ni-30Cr Weld Applications. 2018. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1523349907312233.

    MLA Style (8th edition)

  • Wheeling, Rebecca. "Eutectic Backfilling: A Fundamental Investigation into Compositional Effects on the Nature of this Crack Healing Phenomenon for Ni-30Cr Weld Applications." Doctoral dissertation, Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1523349907312233

    Chicago Manual of Style (17th edition)