Material characterization of additive manufactured metal parts for failure analysis

• Main Author: Seow, Mei Qi
• Other Authors: Li Hua
• Format: Final Year Project
• Language: English
• Published: 2019
• Subjects: Engineering::Mechanical engineering
• Online Access: http://hdl.handle.net/10356/78732
• Institution: Nanyang Technological University

In the recent years, the usage of Selective Laser Melting (SLM) technology has been on a rise in the manufacturing industry due to the capabilities of allowing manufacturers to fabricate parts with higher complexity and lower part count as compared to conventional manufacturing. SLM is a powder based fusion additive manufacturing technique which utilities energy from the laser for the melting of powder layers by layers to form a 3-dimensional (3D) part. SLM fabricated parts have near full density with relatively good mechanical properties. However, various defects such as un-melted powder particles, microcracks, pores are formed during the process, affecting the results of SLM fabricated in tensile testing. Thus, to achieve consistent fabrication of SLM parts for manufacturing industry, the mechanical properties and its microstructure is to be examined to ensure that it is suitable for its intended use. Therefore, the primary focus of this project is to investigate on the SLM fabricated samples within a same built with fixed SLM process parameters. The samples are tested for its mechanical properties via tensile testing, there are differences in mechanical performance such as YS, UTS, EL, ROA is observed. This resulted in the differences of microstructural defects, fractography and porosity analysis using Scanning Electron Microscope (SEM) and Optical Microscope (OM). From the result, the samples with extensive defects including larger amount of un-melted particles, larger percentage of porosity density resulted in poorer mechanical performance. As well as the positioning of samples on the building plate suggested I the inhomogeneous cooling rate with a built chamber which resulted in the increase presence of columnar grains in samples.