Master of Science, The Ohio State University, 1969, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 1970, Graduate School

Committee: Not Provided (Other) Subjects:

Master of Science, The Ohio State University, 2020, Welding Engineering

High energy density welds are often used in critical applications involving a wide range of structural materials. In most cases, both laser and electron beam welding may be considered for these applications and the ability to use both processes to make comparable welds in terms of both weld profile and microstructure provides considerable process selection flexibility. In this study, autogenous, partial penetration welds on 304 SS, 304L SS, and Ti-6Al-4V were made using both fiber laser and electron beam processes. The main variables of interest, power and travel speed, were varied independently. Beam characterization was performed to determine parameters necessary for similar welding conditions between the two processes. Overfocused electron beams produced a more Gaussian distribution than underfocused beams. Laser beam characterization showed a slight increase in sharp spot size with increasing power, likely due to machine capabilities. Welds were made using sharp focus for laser welds and both a sharp, deflected beam and an overfocused beam for electron beam welds. Depth of penetration varied substantially between process conditions, but a similar trend between processes was observed when comparing area of the fusion zone, suggesting a similar melting efficiency. For defocused electron beam welds, increases in voltage yielded a dip in penetration for increasing power. This was likely due to complications with the machine or the diagnostic tool resulting in a narrower beam at lower voltages. A reduction in melting efficiency was observed in Ti-6Al-4V laser welds as compared to EB welds, likely due to vaporization effects, material properties, or both. Analysis of the depth of penetration for 304L and Ti-6Al-4V laser welds at varying powers and travel speed yielded predictive process maps. Stainless steel alloys showed consistent microstructures with work found in literature for pulsed laser welding. Limited metallographic analysis for Ti-6Al-4V welds was conducte (open full item for complete abstract)

Committee: John Lippold (Advisor); Boyd Panton (Advisor); Carolin Fink (Committee Member) Subjects: Materials Science

Master of Sciences (Engineering), Case Western Reserve University, 2015, Materials Science and Engineering

In this study, a number of established additive manufacturing processes were evaluated for their suitability repairing high-pressure die cast tooling. The processes included in this study are laser hot wire (LHW), electron beam freeform fabrication (EBF3), gas metal arc welding (GMAW), Laser Engineered Net Shaping (LENS®), and direct metal deposition (DMD). To determine each process' suitability, blocks of maraging 250 steel were deposited on H-13 base metal. The results show that the maraging deposits are capable of providing good strength (>160 ksi), toughness (>15 ft-lbs), and hardness (45 HRC) for die tooling applications, but care must be taken to limit the occurrence of defects, particularly porosity. Of the processes tested, the LHW, DMD, and LENS® processes had the best balance of deposit properties. However, additional work will be required to optimize the processing parameters for each process.

Committee: David Schwam (Advisor); John Lewandowski (Committee Member); Gerhard Welsch (Committee Member) Subjects: Engineering; Materials Science; Metallurgy