Solidification Cracking and Ductility-Dip Cracking Resistance of Ni-Base Filler Metal 52XL with Tantalum and Molybdenum Additions
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The Ohio State University / OhioLINK
2020
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| Online Access: | http://rave.ohiolink.edu/etdc/view?acc_num=osu1575462956102374 |
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ndltd-OhioLink-oai-etd.ohiolink.edu-osu15754629561023742021-08-03T07:13:36Z Solidification Cracking and Ductility-Dip Cracking Resistance of Ni-Base Filler Metal 52XL with Tantalum and Molybdenum Additions Johnson, Luke Metallurgy Materials Science Ni-30Cr alloys are extensively used in the nuclear power industry to mitigate stress corrosion cracking in repair and new construction applications. Depending on the composition, current Nb-bearing filler metals face weldability challenges in the form of solidification cracking or ductility-dip cracking. Due to the nature of the eutectic that forms in the final stages of solidification, it is difficult to avoid both forms of cracking simultaneously. Tantalum has been identified as an alternative eutectic forming element to replace Nb in new filler metal 52XL.In this project, the first commercially produced wire of 52XL was evaluated in terms of its solidification cracking resistance as compared to other Ni-base filler metals using Transverse Varestraint Testing (TVT) and Cast Pin Tear Testing (CPTT). 52XL is expected to be resistant to solidification cracking under low and medium restraint conditions based on a maximum cracking distance (MCD) in the TVT of less than 1 mm and a pin length cracking threshold used in CPTT that is greater than 0.625 inches. Computational Scheil modeling in ThermoCalc was used to study the weld solidification behavior of 52XL as a function of Ta and Mo additions. Eutectic content, solidification path, and phase composition were evaluated in 52XL variants with 2-4 wt% Ta and 0-4wt% Mo. Solidification behavior was also investigated using differential thermal analysis (DTA). Computational modeling did not correlate well with DTA results which may have been a result of poor experimental design. Modeling also predicted significantly high eutectic formation which did not correlate to STEM analysis done by previous researchers.The effects of molybdenum on the ductility-dip cracking resistance of 52XL were analyzed. A design of experiment (DOE) using Scheil solidification modeling for a total of 21 compositions with varying levels of C, Ta, and Mo was conducted. Microstructural analyze of 52XL with and without molybdenum was performed with light optical micrographs (LOM) and scanning electron microscope (SEM) images. As-solidified weld metal samples showed Mo additions decreased the size of M23C6 precipitates but did not increase eutectic content. Additional samples were heat treated to simulate secondary carbide formation in Ta-bearing filler metals. Mo additions appeared to increase secondary carbide formation which may decrease grain boundary movement and increase DDC resistance. 2020-10-01 English text The Ohio State University / OhioLINK http://rave.ohiolink.edu/etdc/view?acc_num=osu1575462956102374 http://rave.ohiolink.edu/etdc/view?acc_num=osu1575462956102374 unrestricted This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws. |
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NDLTD |
| language |
English |
| sources |
NDLTD |
| topic |
Metallurgy Materials Science |
| spellingShingle |
Metallurgy Materials Science Johnson, Luke Solidification Cracking and Ductility-Dip Cracking Resistance of Ni-Base Filler Metal 52XL with Tantalum and Molybdenum Additions |
| author |
Johnson, Luke |
| author_facet |
Johnson, Luke |
| author_sort |
Johnson, Luke |
| title |
Solidification Cracking and Ductility-Dip Cracking Resistance of Ni-Base Filler Metal 52XL with Tantalum and Molybdenum Additions |
| title_short |
Solidification Cracking and Ductility-Dip Cracking Resistance of Ni-Base Filler Metal 52XL with Tantalum and Molybdenum Additions |
| title_full |
Solidification Cracking and Ductility-Dip Cracking Resistance of Ni-Base Filler Metal 52XL with Tantalum and Molybdenum Additions |
| title_fullStr |
Solidification Cracking and Ductility-Dip Cracking Resistance of Ni-Base Filler Metal 52XL with Tantalum and Molybdenum Additions |
| title_full_unstemmed |
Solidification Cracking and Ductility-Dip Cracking Resistance of Ni-Base Filler Metal 52XL with Tantalum and Molybdenum Additions |
| title_sort |
solidification cracking and ductility-dip cracking resistance of ni-base filler metal 52xl with tantalum and molybdenum additions |
| publisher |
The Ohio State University / OhioLINK |
| publishDate |
2020 |
| url |
http://rave.ohiolink.edu/etdc/view?acc_num=osu1575462956102374 |
| work_keys_str_mv |
AT johnsonluke solidificationcrackingandductilitydipcrackingresistanceofnibasefillermetal52xlwithtantalumandmolybdenumadditions |
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