Date of Award

Summer 2018

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Metallurgical Engineering

Committee Chair

KV Sudhakar

First Advisor

Ronald White

Second Advisor

Bruce Madigan

Third Advisor

Ronda Coguill

Abstract

Laser powder bed fusion additive manufactured 316L stainless steel specimens were evaluated to establish a baseline for future research in determining an optimized energy density and build orientation. Test specimens were printed at various energy densities. At each energy density, tensile and fatigue specimens were printed at 0o (longitudinal), 45o, and 90o (transverse) orientation to the build plate. Tensile and high cycle fatigue tests were performed then representative fracture surfaces were analyzed. The apparent melt track and dendrite size were evaluated using grain analysis software. Static loading of the tensile specimens showed a marginal difference in UTS for specimens with a longitudinal and 45o orientation to the build plate. The transverse orientation was more variable due to the UTS response to the quality of fusion between melt track layers. The energy density affected the fatigue as well. Typically, the medium energy density had the most consistent behavior. Fractography revealed a relationship between energy density and melt track fusion. The optimum energy density in this study was determined to be 100 J/mm3, based on the highest transverse UTS, highest fatigue limit, moderate ductility, and moderate volume of lack of fusion defects. Specimens fabricated at a lower energy density had insufficient heat input to achieve good fusion which reduced the transverse UTS, ductility, and fatigue limit. The highest energy density was excessive energy density leading to an increase in defects reducing the transverse UTS and fatigue limit. The UTS was not strongly affected by the defect volume except in the transverse orientation, where a high defect volume reduced the quality of fusion between melt track layers. Keywords:

Comments

A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Metallurgical and Mineral Processing Engineering

Download

Included in

Metallurgy Commons

Share

COinS