College - Author 1
College of Engineering
Department - Author 1
Materials Engineering Department
Degree Name - Author 1
BS in Materials Engineering
Blair London, College of Engineering, Materials Engineering Department
This project aimed to improve the mechanical properties of as-printed additively manufactured Inconel 718 samples using a heat treatment usually used for cast and wrought Inconel 718. The mechanical properties sought to be optimized were yield strength, ultimate tensile strength, elongation, and reduction in area. The property goals were to match or exceed those of cast and heat treated Inconel 718. Wire-fed electron beam direct energy deposition (DED) was used to manufacture the samples, which were then heat treated using the AMS 5663 standard in an inert atmosphere. The samples were then tested in tension to obtain data on their mechanical properties. An as-printed sample was used as the control for the experiment before testing the heat-treated samples. The microstructures of the samples were then examined to determine the cause of any differences in the mechanical properties of the samples. The heat-treated samples displayed an increase in strength that matched the strength of cast Inconel 718. This increase in strength was caused by grain coarsening, dissolution of the Laves phase at layer interfaces, and precipitation of the δ phase and MC carbides in the gamma matrix (γ). The generalized heat treatment improved the mechanical properties of the DED Inconel 718, but the process could be improved. Future work should focus on tailoring the heat treatment for the specific manufacturing route and application of the material to optimize the mechanical properties even more. For example, high levels of the δ phase in the γ matrix signaled an overaging of the material that could have been prevented with a different heat treatment cycle.