Study of Additive Manufacturing of Hastelloy X Using Plasma Arc Welding Technology

Abstract

Plasma arc welding (PAW) was implemented for additive manufacturing (AM) of Hastelloy X wire due to its potential to produce thin-wall structures for a high-temperature resistance of Hastelloy X. Single-layer beads were deposited to study and optimize the effects of eight process parameters (arc length, nozzle size, built-in and trailing shielding gas flow rate, wire feed rate, travel speed, current, and linear energy density). In the meantime, an additional trailing shielding mechanism was introduced to reduce surface oxidation while maintaining acceptable geometry for multiple-layer deposition. A multiple regression method was used to determine the influence of these parameters on the extent of oxidation, geometry, height and width of bead. The optimized parameters were then used for multiple-layer depositions where complete fusion without visible voids was achieved. However, some interface separations were found due to the minor surface oxidation between layers. Equiaxed-to-columnar grain structure was also observed along the deposition direction where molybdenum carbides were present. The final samples were further evaluated by hardness test. A superior isotropic hardness (HV 218) was achieved on the multiple-layer sample when compared with wrought Hastelloy X (HV 179). Multiple-layer depositing techniques were satisfactorily developed in this study. The optimized PAW process was proven to prevent overheating during starting and ending portion of the deposition. Heat reduction for each successive layer was also determined to produce a wall structure.iii ACKNOWLEDGEMENT I would like to express my greatest gratitude to my thesis supervisors Dr. Xiao Huang and Dr. Hanspeter Frei. I would not be able to complete this work without your guidance and patience.I must also thank Shahryar Shahryari Fard, the staff in the machine shop, the technologists in the MAE department, and other students for their help and assistance during the past two years.Thanks to my friends for being with me all the time no matter where they are. Finally, the credit belongs to my family, and I am so lucky to have you in my life -my forever love. iv TABLE OF CONTENT ABSTRACT .

Study on mechanical properties of nickel-based tungsten carbide cladding layer based on plasma cladding process

“…Compared to the cladding current of 130-140 A, when the cladding current was 150 A, the tungsten carbide particles within the cladding layer were finer and were distributed throughout the central and lower regions of the cladding stratum, playing a dispersion strengthening role. Meanwhile, the smaller tungsten carbide in the cladding layer could prevent grain growth and refine the cladding layer structure [11] . When the cladding current was 160 A, the cladding layer hardness reached its maximum value.…”