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Inertia Friction Welded Ni-Base Superalloys: Process Examination, Modeling and Microstructure

Mahaffey, David
http://rave.ohiolink.edu/etdc/view?acc_num=osu1462525317

Abstract Details

2016, Doctor of Philosophy, Ohio State University, Industrial and Systems Engineering.
Inertia friction welding of Ni-base superalloys is of increasing importance for future designs of turbine engines where the overall pressure ratio and operating temperatures are increased in an effort to improve efficiency. Ni-base superalloys are chosen for the hottest sections due to their inherent ability to retain good strength levels to very high fractions of their melting point. As model systems, the Ni-base superalloys LSHR and Mar-M247 were chosen for further welding and investigation. The LSHR is a powder-metallurgy alloy that is a surrogate for a bore material in a multi-alloy disk system. The Mar-M247 is a coarse-grain cast alloy that is a surrogate for a rim alloy. As the strength retention at elevated temperatures is advantageous for engine applications, it is disadvantageous for the production of sound welds. This effectively reduces the size of the processing window for these alloys. These alloys that are high in gamma prime formers are also prone to weld cracking issues. These factors make it necessary to utilize a process model to improve weld outcomes and reduce the amount of trial-and-error experimentation. Finite element modeling techniques and experimental weld process examination have led to insights into the complex interplay between the weld process parameters and their impact on post-weld microstructure, bond quality & character as well as mechanical properties. In effort to improve upon the predictive capability of the finite element process model, a number of weld parameters were examined. A minimum energy input bond criteria was formulated along with empirical relationships between the process parameters and weld behavior. Key input data for finite element process modeling was shown to include flow stress, coefficient of friction, and weld process efficiency. Strategies to estimate appropriate values for these key parameters were demonstrated and validated within the process model. The methodology to identify appropriate welding parameters, as well as their relative importance, was determined based on weld-trial data and resultant bond quality. The Ni-base superalloys LSHR and MarM247 were welded under varying conditions to provide experimental validation data. The finite element model results indicated the importance of the weld variables outlined above for accurate prediction of weld quality and upset. The investigation showed that the weld kinetic energy was not a sufficient criterion to set weld process parameters, and the effects of the efficiency of the weld equipment can have a profound impact on both the interpretation of model results and weld outcomes. It was also established that the weld upset behavior changes as a function of the energy multiplied by axial load. This parameter was also related to a minimum upset criterion.
Rajiv Shivpuri (Advisor)
Hamish Fraser (Committee Member)
Wei Zhang (Committee Member)
171 p.
Industrial Engineering; Metallurgy
Ni base superalloys; inertia friction welding; finite element model; weld process efficiency

Recommended Citations

Citations

  • Mahaffey, D. (2016). Inertia Friction Welded Ni-Base Superalloys: Process Examination, Modeling and Microstructure [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1462525317

    APA Style (7th edition)

  • Mahaffey, David. Inertia Friction Welded Ni-Base Superalloys: Process Examination, Modeling and Microstructure. 2016. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1462525317.

    MLA Style (8th edition)

  • Mahaffey, David. "Inertia Friction Welded Ni-Base Superalloys: Process Examination, Modeling and Microstructure." Doctoral dissertation, Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1462525317

    Chicago Manual of Style (17th edition)

osu1462525317
290
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This open access ETD is published by The Ohio State University and OhioLINK.