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Solidification Cracking Performance and Metallurgical Analysis of Filler Metal 82

Orr, Michael Romanoff
http://rave.ohiolink.edu/etdc/view?acc_num=osu1470067177

Abstract Details

2016, Master of Science, Ohio State University, Welding Engineering.
The main objective of this research is to investigate and eventually optimize the solidification cracking resistance of filler metal ERNiCr-3 (FM 82) in thick-section, highly-restrained, hot wire automatic gas tungsten-arc welding (AGTAW-HW) weld deposits used on reactor vessels in the nuclear energy industry. This investigation was achieved with experimental verification of cracking responses of three FM 82 heats using the Cast Pin Tear Test (CPTT), metallurgical/chemical analysis of each heat, and computational analysis. An intentional nitrogen addition study was conducted to observe the effect of increased weld metal N on solidification cracking susceptibility of FM 82. Experimentally, results were considered using the CPTT with varying heats of ERNiCr-3 exhibiting either superior or poor solidification cracking resistance behavior. A verification study was implemented using the CPTT and its designated procedure with three heats of FM 82 that were previously tested. Excellent correlation results showed accuracy and repeatability of the CPTT process. Quantitatively, zero-pin deviations were found at the lower cracking threshold (LCT) of each heat. The LCT is designated as the highest pin length to exhibit 0% and is the main ranking criterion of solidification cracking susceptibility. Qualitatively, the results proved to verify the same ranking of solidification cracking susceptibility as the previous study—this ranking also mimics what is observed in production mockups. Scanning electron microscope (SEM) imaging of fracture surfaces exhibited classic solidification fracture morphology to ensure failure mode. Additional work was completed using the CPTT for two dilution studies (10wt% and 25wt %) of a “resistant” heat by a “susceptible” heat. It was observed that 10% dilution of Heat B by Heat A reduced the LCT by one pin-length, whereas 25% dilution reduced it by three pin-lengths. Furthermore, computational thermodynamic software, Thermo-CalcTM, was utilized to determine solidification temperature ranges and terminal phase formations of the FM 82 heat chemistries. This technique constituted a Scheil simulation which estimate alloying segregation behavior during solidification and phase stability after welding. For ease of comparison, one resistant heat (Heat B) was compared against one susceptible heat (Heat A). Heat B was predicted to have a solidification temperature range (STR) of 216°C and 0.1985 volume fraction NbC upon solidification to 99% solid. Heat A was predicted to have a lower STR (203°C) and higher volume fraction NbC (0.2822) upon solidification to 99% solid. Lastly, intentional nitrogen additions were included to see the effects the interstitial has on the susceptibility to solidification cracking of a FM 82 heat. Weldability testing included CPTT of a resistant heat welded with additions of 0.2, 0.4, 1, and 5 vol% N2 in the shielding gas mixture. SEM/EDS techniques were utilized to determine which constituents form based on the nitrogen content of the gas mixture. MX-type precipitates rich in Nb and Ti were found both in grain boundaries and in regions throughout the matrix. Although TEM work was not done to confirm this, the literature determines these MX precipitates to be (Nb,Ti)(C,N).
John Lippold, Dr. (Advisor)
Antonio Ramirez, Dr. (Committee Member)
177 p.
Metallurgy
ERNiCr-3; Filler Metal 82; Cast Pin Tear Test; Solidification Cracking

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Citations

  • Orr, M. R. (2016). Solidification Cracking Performance and Metallurgical Analysis of Filler Metal 82 [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1470067177

    APA Style (7th edition)

  • Orr, Michael. Solidification Cracking Performance and Metallurgical Analysis of Filler Metal 82. 2016. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1470067177.

    MLA Style (8th edition)

  • Orr, Michael. "Solidification Cracking Performance and Metallurgical Analysis of Filler Metal 82." Master's thesis, Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1470067177

    Chicago Manual of Style (17th edition)

osu1470067177
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This open access ETD is published by The Ohio State University and OhioLINK.
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