Year

2018

Degree Name

Doctor of Philosophy

Department

School of Mechanical, Materials, Mechatronic and Biomedical Engineering

Abstract

In recent years, significant progress has been made in the development of the Wire Arc Additive Manufacturing (WAAM) processes due to its economically produced large-scale metal components with relatively high deposition rate. As WAAM has evolved, a wide range of materials have become associated with the processes and applications. Today, producing high-quality WAAM products and improving their potential service life are still a challenge. This dissertation focuses primarily on critical issues and methodologies to improve quality performance of component fabricated by WAAM technique.

The research was the first attempt to study the WAAM process from complex thermal behaviour point of view. It is found that due to the influences of thermal accumulation, the interlayer’s surface oxidation, bead geometry, microstructural evolution, grain size, and crystalline phase vary along the building direction of the as-fabricated wall, which creates variations in arc shape, metal transfer behaviour, mechanical properties and fracture features. Additionally, the corrosion behaviour within the WAAM-processed part is anisotropic due to corresponding anisotropy in microstructure, phase structure, grain size and orientation. The research provides a better understanding of the effects of heat accumulation behaviour on deposition stability and material properties during WAAM process, which benefits future process control, improvement, and optimization.

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