Advancement in wire-fed directed energy deposition process by enhancing ease of part removal and quality

Abstract

The experimental work presented in this thesis explores innovative substrate designs and methods to enhance part quality in wire-fed directed energy deposition processes (WF-DED). The WF-DED processes can fabricate fully dense metal parts with a high deposition rate and efficient material utilisation, compared to its counterpart powderbased processes, which suffer from poor catchment efficiency, low deposition rate, high cost, and intricate handling. This thesis identifies limitations that hinder the widespread adoption of WF-DED processes. Novel substrate designs, including the pillar, weld stub (WSS), and swarf substrate, are proposed to facilitate part removal, reduce machining requirements, provide support for overhang deposition, and allow the deposition of complex parts. The pillar substrate facilitates easy part separation, leaving minimal machining requirements for fused pillar units and enabling overhangs/non-planar feature deposition. The WSS, along with repurposing welding waste, improves non-planar feature resolution and supports the deposition of complex parts such as coil spring. The swarf substrate, which repurposes the waste metal chips, enhances substrate disintegration, making it suitable for depositing complex components such as alloy wheel prototypes, thin spokes, and coil springs. In order to ensure the deposition quality parts deposited on these substrates were compared with conventional solid substrates for the low alloy steel/Inconel 625.