Microstructural characterization and mechanical properties of 3D-printed co-cr-mo parts by electron beam melting (EBM)

• Main Author: Muhammad Hanif Bin Abdul Wahab
• Other Authors: Tor Shu Beng
• Format: Final Year Project
• Language: English
• Published: 2016
• Subjects: DRNTU::Engineering::Aeronautical engineering::Materials of construction
• Online Access: http://hdl.handle.net/10356/68731
• Institution: Nanyang Technological University

Electron Beam Manufacturing (EBM), a newly introduced form of additive manufacturing, is gaining more interest in numerous industries due to it’s great potential applications in orthopaedic implants, dental implants and aerospace components. However, little has been done to study its microstructure and how it relates to its physical properties. This study investigates the mechanical properties and its relation to the microstructure of as-built EBM-fabricated CoCr parts of varying thicknesses. The fabricated parts were found to have less than 1% porosity. Microstructural characterization was carried out using Scanning Electron Microscopy (SEM) and the Optical Microscope (OM). It was found that the microstructure consists mainly of face-centred cubic columnar grains as well as continuous carbide thin films at grain boundaries and inter-dendritic regions. Several differences between thick and thin samples’ microstructure were also discussed including thickness of carbide precipitation, presence of nitride precipitation and equiaxed grains in thick samples, difference columnar grain orientation as well as the difference in carbide precipitation found in inter-dendritic regions. The differences found can be mainly attributed to a increased heat input into the thick parts as compared to the thin parts. In addition, tensile and compressive tests were conducted. The parts anisotropic properties when subjected to compressive and tensional load in different load directions were showcased. Furthermore, differences in mechanical properties of thick and thin samples were found with thicker samples showcasing better ultimate tensile strength but weaker yield strength. The microstructure property and its relation to the mechanical properties are also discussed.