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Development of a gleeble based test for post weld heat treatment cracking in nickel alloys

Norton, Seth J.
http://rave.ohiolink.edu/etdc/view?acc_num=osu1057177289

Abstract Details

2003, Master of Science, Ohio State University, Welding Engineering.
The purpose of this work was to use a thermo-mechanical simulator to develop a simple test that will quantify susceptibility to the various forms of postweld heat treatment cracking, including stress-relief cracking and strain-age cracking. Materials evaluated include Waspaloy and Alloy 718. Samples are initially given an elevated temperature thermal exposure that simulates the weld HAZ. Upon cooling from elevated temperature, the sample is loaded such that yield strength magnitude stresses are present at room temperature. The sample is then heated to a selected PWHT temperature and held for up to 8 hours. Acquisition of tensile force data during PWHT shows an initial relaxation of stresses, followed by a rise in stress as precipitation reactions proceed. Hot ductility tests were performed at various PWHT temperatures and times. From the reduction in area measurements a mathematical model was developed to relate ductility to PWHT temperature and time. The alloys tested show a significant dip in ductility at elevated temperature. Waspaloy samples exhibited lower ductility at elevated temperatures than did Alloy 718, confirming the higher susceptibility of Waspaloy to strain-age cracking. SEM fractography and optical microscopy were used to analyze the failed samples. Minimum ductility samples revealed ductile intergranular fracture paths in Waspaloy and a tendency for transgranular cracking in Alloy 718. Intergranular micro-cracks were evident in a coarse grained heat affected zone in both alloys. Grain size was shown to effect ductility and fracture mode. Smaller grained simulated HAZ samples exhibited more ductility and a tendency for transgranular ductile fracture. Larger grains resulted in an increase in intergranular fracture and a reduction in elevated temperature ductility. Alloy 718 showed evidence of bending of crystal lattices to accommodate stresses. Both alloys showed indications of an effect of grain boundary orientation on cracking susceptibility.
John Lippold (Advisor)
134 p.
Waspaloy; Alloy 718; strain-age cracking; Gleeble testing; post weld heat treatment cracking; stress-releif cracking

Recommended Citations

Citations

  • Norton, S. J. (2003). Development of a gleeble based test for post weld heat treatment cracking in nickel alloys [Master's thesis, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1057177289

    APA Style (7th edition)

  • Norton, Seth. Development of a gleeble based test for post weld heat treatment cracking in nickel alloys. 2003. Ohio State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1057177289.

    MLA Style (8th edition)

  • Norton, Seth. "Development of a gleeble based test for post weld heat treatment cracking in nickel alloys." Master's thesis, Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1057177289

    Chicago Manual of Style (17th edition)

osu1057177289
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© 2003, all rights reserved.
This open access ETD is published by The Ohio State University and OhioLINK.