Theses and Dissertations

Issuing Body

Mississippi State University


Stone, Tonya W.

Committee Member

Shamsaei, Nima

Committee Member

Doude, Haley R.

Committee Member

Priddy, Matthew W.

Date of Degree


Document Type

Graduate Thesis - Open Access


Mechanical Engineering

Degree Name

Master of Science (M.S.)


James Worth Bagley College of Engineering


Department of Mechanical Engineering


Inconel 718 is a nickel-based superalloy with a series of superior properties, such as high strength, creep-resistance, and corrosion-resistance. Additive manufacturing (AM) is appealing to Inconel 718 because of its near-net-shape production capability to circumvent poor machinability. However, AM parts are prone to detrimental porosity, reducing their fatigue resistance. Thus, further understanding of AM fatigue behavior is required before widespread industrial use. The microstructural and fatigue properties of heat treated AM Inconel 718, produced using Laser Engineered Net Shaping (LENSTM), are evaluated at room and elevated temperatures. Fully reversed, strain-controlled fatigue tests were performed on cylindrical specimens at strain amplitudes of 0.001 to 0.01 mm/mm. Fracture surfaces were inspected using a scanning electron microscope (SEM). Heat treatment caused initial dendritic microstructure to mostly reorm into an equiaxed grain structure. AM specimens experienced reduced fatigue life in testing as compared to wrought material due to inclusions or pores near the surface