Abstract

Electron beam freeform fabrication (EBF³) is a rapid metal deposition process that works efficiently with the wieldable alloy Inconel 718 (IN 718). EBF³ is a developing additive manufacturing (AM) process that can manufacture IN 718 parts directly from computer aided design (CAD) data. EBF³ can produce parts significantly faster and more energy efficient than competing IN 718 AM technologies. The EBF³ process utilizes metal wire feedstock which is induced into a molten pool using a focused electron beam in a vacuum environment. This allows parts to be built layer by layer, creating intricate shapes that can be produced cheaper and faster than traditionally manufactured IN 718 parts. Furthermore, it allows traditionally manufactured parts to be modified as additional form is added to them using EBF³. Multiple industries rely on IN 718 parts and can utilize this technology including aerospace engineering, oil refinery, nuclear power generation, and food processing.A main drawback of EBF³ is the lack of knowledge of the effect different EBF³ build techniques will have on the properties of the deposited materials. Most of the reliable data on the mechanical properties relate to a linear build-up strategy and focus on the mechanical properties in the deposition direction (DD). There is no data related to other build-up techniques such as rotation build-up or transitional builds from forged material to EBF³ material. Reliable data on the behavior and microstructure of EBF³ material in a direction other than the DD is also difficult to find. Previous studies showed build-up height influenced mechanical properties but its role is not fully understood yet. This paper presents the mechanical properties and microstructure of an IN 718 plate built using a EBF³ rotational build-up strategy through utilizing a forged plug in the center. The tensile properties of samples at the transition from forged to EBF³ material showed higher ductility and reduced strength than pure EBF³ material. This is likely due the influence of the forge material in one half of the specimen. Samples taken at approximately 15 degree increments from 0 to 90 degrees rotation to the DD in the additive portion of the plate were subjected to tensile testing. Along the build height, or the transverse direction (TD), the lowest strength was demonstrated and the TD aligned strongly to a <001> texture. Samples 45 degrees to the DD showed the greatest strength due to their preference for aligning to a <111> texture. Samples low on the build height demonstrated a higher strength than those on the top and displayed grain structures along the TD which were long, linear, and narrow across multiple deposition layers.

Degree

College and Department

Ira A. Fulton College of Engineering and Technology; Technology

Rights

http://lib.byu.edu/about/copyright/