Abstract

Excellent weldability and high temperature stability make Inconel 718 (IN718) one of the most desired alloys to be produced by additive manufacturing (AM). Within the flourishing field of AM technology, laser powder bed fusion (LPBF) is a popular prospective candidate capable of fabricating complex and near net-shape engineering components that traditional manufacturing methods cannot accomplish. In this study, the effects of processing parameters on the relative density and microstructure was investigated. Gas atomized IN718 powders were used to fabricate cuboidal specimens via LPBF for metallographic characterization. The specimens were printed with independently varied laser power (125 - 350 W), laser scan speed (200 - 2200 mm/s), and laser scan rotation (0 - 90 degrees). Archimedes' method, optical microscopy, and scanning electron microscopy were employed to assess the influence of LPBF parameters on part density and microstructure, respectively. In general, relative density greater than 99.5% was achieved for a wide range of energy density between 50 and 100 J/mm^3. At higher laser powers, larger processing windows to produce high density parts were documented. Microstructural features including melt pool geometry, lack of fusions defects, keyhole porosity, and grain structure were examined and correlated to a wide range of LPBF parameters. The cellular microstructure within grains was observed to decrease with increasing laser scan speed. Based on the measurement of cellular structures and Rosenthal models, cooling rate in LPBF was estimated to be in the order of 10^5 - 10^7 K/s.

Notes

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Graduation Date

2020

Semester

Fall

Advisor

Sohn, Yongho

Degree

Master of Science in Materials Science and Engineering (M.S.M.S.E.)

College

College of Engineering and Computer Science

Department

Materials Science and Engineering

Degree Program

Materials Science and Engineering

Format

application/pdf

Identifier

CFE0008336; DP0023773

Language

English

Release Date

12-15-2020

Length of Campus-only Access

None

Access Status

Masters Thesis (Open Access)

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