Graduation Semester and Year

2020

Language

English

Document Type

Thesis

Degree Name

Master of Science in Mechanical Engineering

Department

Mechanical and Aerospace Engineering

First Advisor

Narges Shayesteh

Abstract

Inconel 718 (i.e., IN718) is a nickel-based superalloy that exhibits outstanding tensile and impact-resistant properties, along with good high-temperature corrosion resistance. However, the machinability is poor due to the high stiffness of IN718. Therefore, additive manufacturing provides an effective solution to overcome the work hardening. Selective laser melting (SLM) is the most common powder-bed additive manufacturing technique designed to use a high power-density laser to melt and fuse the metallic powder to fabricate functional parts with high accuracy. However, the accuracy and the functional properties of the fabricated parts are greatly dependent on the process parameters. Thus, depending on the desired properties, the process parameters for a given material need to be optimized for improving the overall reliability of the SLM devices. The processing parameters that control the SLM process comprise of the laser power, scan speed, hatch spacing, and layer thickness. These process parameters are dependent on each other and therefore making the task of optimizing the process parameters an important one. One of the biggest advantages of optimizing these above-mentioned process parameters is it enables us to control the microstructure as per the requirements. It is important to regulate the microstructure to control the mechanical properties such as tensile strength, yield strength, impact intensity and toughness, as it will directly influence the grain and melt pool distribution in the fabricated parts. As the number of combinations increases, the probability of failure of these additively manufactured parts increases exponentially. As all the process parameters are inter-dependent on each other, finding an optimum value to suit the requirement and render the best build quality both in terms of computer-aided design (CAD) vi accuracy and desired metallurgical properties is necessary. Thus, it is essential to determine and establish the optimum combination of values for process parameters. Design of Experiments (DOE) methodology was used to construct an experiment that evaluated the CAD deviation, composition, hardness and roughness of SLM fabricated IN718 against the three critical processing parameters: laser power, scanning speed and hatch spacing. This work primarily focusses on the effect of various process parameters on the metallurgical properties and mechanical properties of Inconel 718 parts fabricated on an EOS M290 machine.

Keywords

EOS M290, Process parameters, IN718, DOE, SLM

Disciplines

Aerospace Engineering | Engineering | Mechanical Engineering

Comments

Degree granted by The University of Texas at Arlington

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