Doctor of Philosophy, The Ohio State University, 1984, Graduate School

Committee: Not Provided (Other) Subjects: Engineering

Doctor of Philosophy, The Ohio State University, 1981, Graduate School

Committee: Not Provided (Other) Subjects: Engineering

Doctor of Philosophy, The Ohio State University, 2023, Welding Engineering

Duplex stainless steels (DSS) are extensively used in heavy industry, such as Oil and gas, pulp and paper, and chemical, due to their remarkable corrosion resistance, yield strength, and toughness. The most corrosion-resistant DSS subgroups, super duplex stainless steels (SDSS) with Pitting Resistance Equivalent numbers (PREn) of 40-48, and the hyper duplex stainless steels (HDSS) with a PREn over 48, are highly alloyed. Additions of Cr and Mo provide better PREn but also promote intermetallic phases such as the chi and sigma phases. These intermetallics form when the material is exposed to temperatures between 600oC – 1100oC. It is known that even small volumetric fractions of the sigma phase severely reduce the material's corrosion resistance and mechanical performance. A dedicated study on sigma phase formation kinetics was developed to control sigma phase presence in these specific alloys. A field studied but not yet completely connected between scientific research and industrial applications. Fundamental aspects of sigma phase kinetics were analyzed, computationally modeled, and experimentally validated. As a result of these efforts, the interface area per unit of volume was revealed as a critical microstructure factor for the sigma phase kinetics. The resultant model's efficacy was further evaluated by building GTAW cladded mockups, and investigation into this material's mechanical and corrosion performance further expanded on the impacts of the sigma phase. A Gleeble® system was used to develop experimental time temperature transformation (TTT) maps on SDSS and HDSS filler metals for sigma phase precipitation kinetics. Classical nucleation theory was then implemented on the CALPHAD-based kinetics model. In this model, the interfacial energy and nucleation sites were identified as the kinetics parameters to adjust the model based on experimental data. The sigma phase kinetics continuous cooling transformation CCT curves were calculated using the additiv (open full item for complete abstract)

Committee: Antonio Ramirez (Advisor); Stephen Niezgoda (Committee Member); Carolin Fink (Committee Member) Subjects: Engineering; Materials Science; Mechanical Engineering

Master of Science, The Ohio State University, 2017, Welding Engineering

Oil reserves off of the coast of Brazil have been discovered under a geological layer of salt. These pre-salt sea oil fields present high material requirements for extraction. The oil itself is high in H2S and other contaminants that make it extremely corrosive. The reserves are below 2 km water, 2km rock, and 2km requiring a stronger pipeline material. X65 pipe internally clad with Ni-based Alloy 625 was chosen for the risers and pipelines to meet these requirements. Joining of these pipelines will occur on-shore, after which the pipes will be loaded onto ships by being reeled onto spools with diameter of 20m. A high deposition rate process is required to make production efficient. The welds cannot be post-weld heat treated (PWHT) and their yield strength must over-match the base metal's by 100 MPa (550 MPa), so that plastic strain occurs in the base metal, not the weld. The yield strength requirement is determined by DNV-OS-F101, a standard for offshore pipeline systems [1]. The primary issue is that weld consumables that meet this strength requirement have a higher melting point than Alloy 625. The increased energy required to melt the consumable results in greater melting of the substrate and increased dilution. If a low alloy steel were utilized, the increased dilution from Alloy 625 results in extensive solidification cracking in the weld metal. From a fundamental perspective, this project is about welding a higher melting point consumable over a lower melting point substrate. The objective of this project was to evaluate the applicability of Duplex and Super Duplex Stainless Steel (DSS, SDSS) filler metals for welding of X65 steel pipes internally clad with Alloy 625 utilizing low heat input Gas Metal Arc Welding (GMAW) process. The problem of solidification cracking in welding with higher melting point consumable over lower melting point substrate was addressed by developing a comprehensive consumable selection and evaluation procedure. The latter includ (open full item for complete abstract)

Committee: Boian Alexandrov Ph.D. (Advisor); Carolin Fink Ph.D. (Committee Member) Subjects: Engineering; Materials Science

Doctor of Philosophy, The Ohio State University, 1982, Graduate School

Committee: Not Provided (Other) Subjects: Engineering

Doctor of Philosophy, The Ohio State University, 1981, Graduate School

Committee: Not Provided (Other) Subjects: Engineering

Doctor of Philosophy, The Ohio State University, 1979, Graduate School

Committee: Not Provided (Other) Subjects: Engineering

Doctor of Philosophy, The Ohio State University, 1975, Graduate School

Committee: Not Provided (Other) Subjects: Engineering

Doctor of Philosophy, The Ohio State University, 1974, Graduate School

Committee: Not Provided (Other) Subjects: Engineering

Master of Science, The Ohio State University, 2009, Welding Engineering

Friction stir welding has recently become an attractive process for the joining of steels. Interest in using this welding process to join steels has become popular due to advancements in friction stir welding tool development. Wear resistant - high temperature tools have been developed, which allow friction stir welding of high melting temperature materials. One such material the U.S. Navy is interested in joining with friction stir welding is a high-strength low-alloy steel (HSLA-65). The U.S. Navy plans to replace the current ship haul steel, DH-36, with HSLA-65, but conventional arc welding processes result with major distortion. A post-flame straitening process must be used to solve the distortion problem. Friction stir welding of HSLA-65 would result with less distortion, which would avoid subjecting the material to the flame straitening process. The work presented here on friction stir welding of HSLA-65 is a continuation of previous investigation conducted by Norton and Sinfield (1; 2). From these previous two studies, it was suggested that austenitic stainless steel be friction stir welded to observe the high temperature behavior of the stir zone material. During this investigation Type 310 stainless steel was friction stir welded to observe the resulting microstructure. A preheating method was tested during the friction stir welding of Type 310 stainless steel. Heat generation from frictional heating in austenitic stainless steel is difficult due to the low thermal conductivity. This is one of the reasons which contribute the difficulties of friction stir welding Type 310 stainless steel. The preheating method was used with successful results. A visually acceptable weld was produced with minimal weld discontinuities and the discontinuities which were present originated from embedded thermocouples. Friction stir welds were also conducted on HSLA-65 to determine the effects of various weld parameters on the resulting microstructure. A high and low tool rot (open full item for complete abstract)

Committee: John Lippold PhD (Advisor); Sudarsanam Babu PhD (Committee Member) Subjects: Engineering; Materials Science

Master of Sciences (Engineering), Case Western Reserve University, 2010, Materials Science and Engineering

Historically it has been very difficult to harden the surface of stainless steels without the loss of corrosion resistance. A novel low temperature carburization process developed by Swagelok Co. which greatly improves the wear resistance of stainless steel has accomplished this feat. This project has studied the friction and wear behavior of low temperature carburized AISI 316L; 1.) Sliding against hard materials, 2.) Sliding under a range of contact stresses and sliding speeds, and 3.) The relationship of wear resistance to the properties of the surface hardened region. It was found that low temperature carburization provided an immense improvement in wear resistance when sliding against hard materials, and this improvement is maintained under stresses and sliding speeds that are too severe for non-treated stainless steels. Furthermore, the improvement in wear resistance was found to be heavily dependent on the hardness and thickness of the case hardened region.

Committee: Arthur Heuer PhD (Advisor); Gary Michal PhD (Committee Member); Frank Ernst PhD (Committee Member); Gerhard Welsch PhD (Committee Member) Subjects: Materials Science

Master of Science, The Ohio State University, 2008, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 1963, Graduate School

Committee: Not Provided (Other) Subjects:

Doctor of Philosophy, The Ohio State University, 2022, Welding Engineering

Stainless steel interlayers for resistance spot welding of a 1.6 mm thick AlSi coated 2000 MPa UTS press hardened boron steel (PHS) and a 2.0 mm thick 6022-T4 aluminum alloy were investigated to improve joint performance. Finite element modeling (FEM) of resistance spot welding was used to determine the interlayer's impact on joint interfacial temperature and weld nugget. Foil and Laser Powder Bed Fusion (L-PBF) and interlayer deposition processes were studied for austenitic and ferritic grade stainless steels. CALPHAD-based simulations were also explored to determine the effects of Cr on forming FeAl3 intermetallic compound (IMC). The implementation of stainless steel interlayers significantly improved the mechanical performance of the joint, with the foil 430 interlayers experiencing 6.6 kN of peak force and 1.9 J of fracture energy at peak force. The intermetallic thickness was assessed for each interlayer deposition, with each method experiencing a noticeable reduction in thickness associated with a no interlayer condition. A fracture surface and energy-dispersive x-ray spectroscopy (EDS) analysis was conducted on the intermetallic-rich regions to determine the IMC composition. Also, a joining method involving ultrasonic metal welding (UMW) plus resistance spot welding (RSW) was evaluated for dissimilar metal joining of aluminum to steel. A thin Al insert is first bonded to a steel sheet using a solid-state procedure. With key welding parameters, UMW of 250 µm ferritic and austenitic stainless steel foil interlayers was determined. Higher ultrasonic welding energies are produced over welded joints, while lower energy inputs are produced under welded conditions. The use of interlayers demonstrated higher joule heating and aluminum bonding diameters when characterizing the dynamic sheet-to-sheet contact resistance during resistance spot welding (RSW) compared to no interlayer conditions. Uncommonly, the higher temperatures experienced in the interlayer jo (open full item for complete abstract)

Committee: Antonio Ramirez (Advisor); Avraham Benatar (Committee Member); Hamish Fraser (Committee Member) Subjects: Engineering

Master of Science (MS), Ohio University, 2017, Biomedical Engineering (Engineering and Technology)

Microbiologically influenced corrosion (MIC), also known as biocorrosion, is a major problem in the oil and gas industry and water utilities. The same problem also exists with biomedical implants inside the human body. Although these medical implants are usually made of corrosion resistant stainless steel alloys or titanium, they still can experience MIC. MIC problems that occur on implants can be even worse sometimes because some places inside the human body (e.g., mouth) contain more bacteria and are more ideal growth environments than pipelines. Among all the microorganisms that cause MIC, sulfate-reducing bacteria (SRB) are often blamed because sulfate is ubiquitous in nature. Chapter 1 discussed various MIC issues facing different industries. Chapter 2 provided a review of various microbes that cause MIC problems on carbon and stainless steels.In order to mitigate MIC, the underlying mechanism must be analyzed. The Ohio University MIC Research Group proposed the biocatalytic cathodic sulfate reduction (BCSR) theory, discussed in Chapter 2, which not only explains the bioelectrochemistry of the SRB MIC process but also overcomes the shortcoming of the previous cathodic depolarization theory (CDT) that is only applicable to hydrogenase-positive SRB. Chapter 4 confirmed the BCSR theory with SRB starvation and overfeeding tests using 304 stainless steel. It was confirmed that SRB MIC is due to SRB harvesting electrons from extracellular iron oxidation for sulfate reduction in order to generate energy when there is a local shortage of organic carbon molecules. Chapter 6 investigated the impact of liquid/headspace volume ratio on MIC by Desulfovibrio vulgaris. It was found that a large headspace allowed more H2S to escape from the culture medium to the headspace and this increased culture medium pH, however, did not statistically influence the weight losses of coupons in 100 ml culture medium and in 50 ml culture medium in the 125 ml vials. It was recommended that fu (open full item for complete abstract)

Committee: Tingyue Gu Ph.D (Advisor); Douglas Goetz Ph.D (Committee Member); Monica Burdick Ph.D (Committee Member); Peter Coschigano Ph.D (Committee Member) Subjects: Biomedical Engineering; Chemical Engineering

Doctor of Philosophy, The Ohio State University, 1986, Graduate School

Committee: Not Provided (Other) Subjects: Engineering

Doctor of Philosophy, The Ohio State University, 1986, Graduate School

Committee: Not Provided (Other) Subjects: Engineering

Doctor of Philosophy, The Ohio State University, 1972, Graduate School

Committee: Not Provided (Other) Subjects: Engineering

Doctor of Philosophy, The Ohio State University, 1971, Graduate School

Committee: Not Provided (Other) Subjects: Engineering

PhD, University of Cincinnati, 2024, Arts and Sciences: Chemistry

Carbon nanotubes (CNTs) hold immense promise in various technological applications, yet their efficacy has been hindered by challenges in establishing robust connections with metal surfaces. This study explores novel methods to address this limitation and enhance the electrical conductivity of CNT-metal interfaces. The resultant CNT-metal hybrid consists of strong bonding in between CNTs, and metal has been investigated in various applications such as sensors and energy storage devices. Covalent bond formation between open-ended CNTs and Cu surfaces is explored experimentally and theoretically. Vertical orientation of CNTs relative to the substrate, coupled with carboxylic functional groups on CNTs reacting with aminophenyl linkers on metal surfaces, facilitates amide bond formation at low temperatures. Theoretical analysis reveals bridge-like bond formations between carbon and adjacent Cu atoms, supporting the observed electrical conductivity enhancement. The robustness of covalent bonding is demonstrated through sonication tests. Due to the appealing nature of carbon nanotubes (CNT) in applications, the investigation extended on CNT films bonded to metal surfaces. Utilizing aligned CNT films, chemically covalent bonds are established between CNTs and various metal surfaces, including Cu, stainless steel, Au, indium tin oxide, and Al. Characterization techniques confirm the formation of robust bonds, with scanning electron microscopy validating their stability post-ultrasonication. Enhanced electrode performance suggests potential applications in sensor technology. Further, CNT bonded to metal electrodes were investigated in energy storage applications. Innovative fabrication of CNT-metal electrodes is achieved by forming chemical bonds between vertically aligned carbon nanotubes (VACNTs) and Au metal surfaces using linker molecules. Covalent bonds between CNTs and diazonium-based linker molecules on the Au surface result in highly conductive interfa (open full item for complete abstract)

Committee: Noe Alvarez Ph.D. (Committee Chair); Jianbing Jiang Ph.D. (Committee Member); Hairong Guan Ph.D. (Committee Member) Subjects: Chemistry