Fatigue test and analysis of powder bed fusion printed specimens

• Main Author: Hui, Max Andrew
• Other Authors: Pang Hock Lye, John
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2024
• Subjects: Engineering; Additive manufacturing; 3D printing; Fatigue; 316L stainless steel; Powder bed fusion
• Online Access: https://hdl.handle.net/10356/176487
• Institution: Nanyang Technological University

This Final Year Project (FYP) explores the fatigue performance of vertically printed powder bed fusion (PBF) 316L stainless steel specimens, aiming to identify the combined effects of heat treatment by hot-isostatic pressure (HIP) and post-surface treatments by machining and shot-peening on their fatigue life. With the rising adoption of additive manufacturing in critical applications, understanding the durability of 3D printed components by PBF under cyclic loading becomes imperative. Through extensive tensile and fatigue testing, complemented by surface roughness measurements and fractographic analysis of fracture surfaces, this research reveals significant insights into how the heat-treatment and post-surface treatments influence the mechanical properties and fatigue performance of PBF 316L specimens. The findings indicate that despite the HIP treatment and machined surface condition of the specimens, it did not improve the fatigue resistance, with the as-built 316L specimen exhibiting superior performance. The shot-peening post-surface treatment was found to enhance the fatigue life of the HIPed specimen marginally, yet still inferior to the as-built specimens. The study also discusses the fractographic results of the fractured specimens. It is found that almost all the specimens share the same crack propagation characteristics where the crack initiates from the surface of the specimen. The cause of failure due to un-melted pores and internal defects such as voids could not be determined using the optical and laser microscope. Finally, proposed recommendations and methods for future research were discussed to improve the current methodology and procedures used in this FYP. This work contributes to the growing body of knowledge on the structural reliability of 3D printed materials, offering valuable insights for researchers, engineers, and manufacturers alike.