Microstructural evaluation of laser bed additive manufactured steels

• Main Author: Pee, Ryan
• Other Authors: Matteo Seita
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2020
• Subjects: Engineering::Materials::Metallic materials::Alloys; Engineering::Materials::Material testing and characterization
• Online Access: https://hdl.handle.net/10356/139016
• Institution: Nanyang Technological University

The microstructural properties of Laser Bed Additive Manufactured (AM) Steels produced by Selective Laser Melting (SLM) are evaluated, starting with 316L Stainless Steels and moving on to Duplex Stainless Steels. The effect of the Laser Energy Density(LED)printing parameter is evaluated on the porosity of AM 316L Stainless Steels.LED is found to give an incomplete picture of evaluating porosity, and a process window is recommended for use in addition to LED to design prints with minimal porosity. Next, a discoloration on AM Duplex Stainless Steels produced by SLM is examined with energy dispersive X-ray spectroscopy and found to be caused by oxidation of the samples. Characterization techniques such as optical microscopy, electron backscatter diffraction and hardness testing were performed to evaluate the effect of oxidation. Oxidation is found to promote the formation of acicular ferrite but it does not affect grain size and hardness of the samples. Understanding these microstructural properties will help decrease the failure rate of prints and could lead to greater adoption of AM Steels in industries.