Honors College Theses

Date

2022

Major

Mechanical Engineering (B.S.)

Document Type and Release Option

Thesis (open access)

Faculty Mentor

Dean Snelling

Abstract

This project addresses the effects of oxygen concentration, laser power, and scanning speed on the melt pool geometry of laser-based powder bed fusion (L-PBF) additively manufactured components. A parametric analysis using the substrate alone was conducted to determine a range of desirable laser powers and scanning speeds. The parameter with the more significant effect will be decided upon based on the depth-to-width ratios (D/W) of the resultant laser weld bead. A range of oxygen levels and scan speeds was selected for the next phase. These samples were then be analyzed for depth-to-width ratios. It was expected that higher oxygen concentrations will result in larger depth-to-width ratios due to the reversal of the Marangoni convection and that lower scan speeds and higher laser powers would yield larger depth-to-width ratios due to increased input energy density. It was determined that increased oxygen levels, up to approximately 1.5% oxygen, slower scanning speeds, with a minimum of approximately 300 mm/s, and higher laser powers yielded increasing D/W ratios. Additionally, the similarity between average and median D/W ratios, along with small standard deviations, indicate that the data exhibits acceptable accuracy and precision.

Thesis Summary

This project addresses the effects of oxygen concentration, laser power, and scanning speed on the melt pool geometry of laser-based powder bed fusion (L-PBF) additively manufactured components. A parametric analysis using the substrate alone was conducted to determine a range of desirable laser powers and scanning speeds. The parameter with the more significant effect will be decided upon based on the depth-to-width ratios (D/W) of the resultant laser weld bead. A range of oxygen levels and scan speeds was selected for the next phase. These samples were then be analyzed for depth-to-width ratios. It was expected that higher oxygen concentrations will result in larger depth-to-width ratios due to the reversal of the Marangoni convection and that lower scan speeds and higher laser powers would yield larger depth-to-width ratios due to increased input energy density. It was determined that increased oxygen levels, up to approximately 1.5% oxygen, slower scanning speeds, with a minimum of approximately 300 mm/s, and higher laser powers yielded increasing D/W ratios. Additionally, the similarity between average and median D/W ratios, along with small standard deviations, indicate that the data exhibits acceptable accuracy and precision.

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