Wire arc additive manufacturing of high strength steel

• Main Author: Goh, Samuel Jun Wei
• Other Authors: Zhou Wei
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2023
• Subjects: Engineering::Materials::Material testing and characterization
• Online Access: https://hdl.handle.net/10356/168360
• Institution: Nanyang Technological University

Additive Manufacturing (AM) has been a game-changer in the manufacturing industry by enabling the creation of complex parts with high precision and reduced material waste. This technology has found applications in various industrial sectors, including aerospace, automotive, biomedical, and energy. Of the many AM processes, Wire Arc Additive Manufacturing (WAAM) has emerged as a promising technology for the fabrication of complex and large-scale metal components. This technology offers several advantages over conventional manufacturing processes, including reduced lead time, improved design flexibility, and reduced material waste. Despite its potential, there is still a need to explore and understand the properties and behavior of WAAM-fabricated components which will contribute to its development and application in various industries. This study focuses on the material characterization of WAAM of ER70S-6, which is a widely used welding filler material. The WAAM process was conducted using a Plasma arc welding (PAW) setup with a 1.2 mm diameter wire feed. The microstructure and mechanical properties of the WAAM-deposited ER70S-6 were investigated. The microstructural analysis of the WAAM-deposited ER70S-6 walled structure showed a variation in the microstructure between the top layer and the interior layers. The microstructure of the top layer contains pockets of acicular ferrite while the interior layers have a refined and equiaxed grain structure. Heat treatment was also done for the WAAM-deposited ER70S-6 in the temperature range of 800 °C to 950 °C with two different cooling methods: air-cooling and water quench, and two hold times: 30 minutes and 1 hour. The samples were then studied using optical microscopy and the Vickers hardness test to determine the material properties. The results show that the quenched samples had a higher hardness compared to the as-built material. The hardness only showed a significant increase at temperatures above 900 °C due to the increase in martensite.