Date of Award
Summer 2023
Document Type
Thesis
Degree Name
Master of Science (MS)
Department
Mechanical Engineering
First Advisor
Zhou, Le
Second Advisor
Moore, John A.
Third Advisor
Fournelle, Raymond
Abstract
Powder bed based additive manufacturing has advantages in its ability to make specialized parts with complex geometries. Unfortunately, components made through such processes of suffer from manufacturing defects including porosity. To study pore formation and removal, specimens of Ti-6Al-4V were built at varied levels of laser power, travel speed, hatch spacing, and layer thickness to obtain a variety of initial defect populations. The specimens were then subjected to a hot isostatic pressure (HIP) at 850 °C and 200 MPa to evaluate the low temperature high pressure (LTHP) cycle’s ability to remove pores. Image analysis was used to estimate the relative density of specimens in both the as-built and the post-HIP condition. A visible trend between GED (global energy density) and porosity was identified for a layer thickness of 20 μm, but not when the layer thickness was 40 μm. HIP removed most pores but was less effective at removing faceted pores. Qualitative analysis revealed a moderate change in microstructure. Vicker’s microhardness measurements showed that hardness decreased after HIP. There was a relationship between hardness and GED in the as-built condition, but the post-HIP hardness was nearly uniform.