Electron Beam Melted Parameter Development of Pure Tungsten & Post-Processing Hip and Heat Treatment of Gamma Titanium Aluminide
Pure tungsten is a refractory metal and has been gaining interest for the use in nuclearfusion reactors as a plasma facing material. Titanium Aluminide (TiAl) has been growing inpopularity as a possibly to phase out Nickel based superalloys due to its high specific strength atelevated temperatures. These two materials suffer from poor machinability due to being brittle atroom temperature. Additive manufacturing (AM) is a recently developed manufacturing methodthat is fundamentally different than formative or subtractive. AM is a layer-by-layer process thathas the potential to manufacture metals to a near net shape. Since the AM process is highlyvariable, the process and resulting material properties need to be verified. The goal of this thesiswas to understand the machine parameters that allows processing of these materials. Tungsten isin an early developmental phase; the goal was to find processing parameters that would yield fullydense tungsten. The build substrate and support structures are critical in the production of the finalpart. Energy densities greater than 370 J/mm3 led to ~98% relative density of pure tungsten.Regarding TiAl, the “as built” condition suffers from anisotropy or heterogeneity in themicrostructure, so post processing is highly recommended. The TiAl underwent Hot IsostaticPressing (HIP) and heat treatment to improve the “as built” parameters. Metallography and tensiletests were completed to determine the mechanical properties. The cooling rate of 5°C/min causedthe resulting microstructure to be similar with similar mechanical properties. The microstructurewas nearly fully lamellar which had around 380 MPa yield stress and around 410 MPa ultimatetensile stress. The elongation was less than 1%. These experiments lay the groundwork for futuremanufacturing of brittle materials using electron beam powder bed fusion technology. This provesthat this can be an effective method of manufacturing to produce favorable material properties foruse in their respective applications.
Watanabe, Kurtis Isami, "Electron Beam Melted Parameter Development of Pure Tungsten & Post-Processing Hip and Heat Treatment of Gamma Titanium Aluminide" (2021). ETD Collection for University of Texas, El Paso. AAI28869605.