Laser metal additive manufacturing study of Fe-based amorphous alloys

• Main Author: Siddiq, Jasmine
• Other Authors: Chen Zhong
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2024
• Subjects: Engineering; Materials Science; Additive manufacturing; Bulk metallic glass; EHLA
• Online Access: https://hdl.handle.net/10356/176255
• Institution: Nanyang Technological University

High-speed laser metal deposition (HS-LMD) employs a focused laser to melt and deposit metallic powders, creating components with complex geometries and enhanced mechanical properties. This process is particularly effective for Fe-based bulk metallic glasses (BMGs), which are notable for their exceptional strength, corrosion, and wear resistance. To ascertain the suitability of Fe-based BMG for HS-LMD, comprehensive powder characterization was conducted. This included analysis of particle size distribution, scanning electron microscopy (SEM) for morphology, aspect ratio, apparent density, hall flow rate, and X-ray diffraction (XRD). The XRD analysis was crucial, confirming the amorphous nature of the powder through the identification of a distinctive broad peak. The study meticulously examined how various deposition parameters—laser power, powder mass flow rate (PMFR), shielding gas, and the number of deposition layers—affect the quality of the deposited layers. Special focus was given to surface microcracks, employing cross-sectional analysis to detect cracks, pores, and unmelted particles. A comparative analysis of hardness showed that the deposited Fe BMG layer vastly surpassed the 316L stainless steel substrate, achieving a remarkable hardness of approximately 1114 HV, which indicates a significant enhancement. Subsequent XRD analysis after deposition not only reconfirmed the amorphous phase of the deposited layer but also identified the emergence of crystalline phases, including monoclinic Molybdenum Iron Carbide (Mo6Fe11C5), Hexagonal Cobalt Iron (Fe0.015Co0.985), cubic Chromium Iron Molybdenum (Cr6Mo5Fe18), and cubic Chromium Carbide (Cr23C6).