Open Collections

Paul, Christopher G. M.

University of British Columbia

Additive manufacturing (AM) technologies are invaluable for the manufacturing industry by enabling the repair of high-value components. Utilizing AM technology such as laser-directed energy deposition (L-DED) to repair casting inserts can increase tool life, reduce metal waste, and lower operating costs. Typically, L-DED systems employ a 1–3 mm diameter laser spot to melt feedstock material. However, recently developed micro-spot L-DED systems, if optimized correctly, could enhance repair applications by creating smaller beads and minimizing heat input. This thesis aims to define suitable parameters for a micro-spot L-DED system and apply these parameters to a proof-of-concept repair process for a high-pressure die casting (HPDC) insert. By varying main L-DED printing parameters, the deposition behaviour and process parameters for achieving high-density maraging steel were determined using a micro-spot L-DED system. Analyzing the aspect ratio and dilution relationship of beads defined a processing window for the ideal bead shape. Volumetric samples were then printed, and process parameters which created high-density material (>99%) were selected. Compared to larger laser diameters, the 0.3 mm laser significantly influences bead formation characteristics, weld pool stability, part shape accuracy, and internal defects. Internal defects such as pores and titanium oxide inclusions reduce tensile strength and ductility for this material. Variations in grain structures found throughout the deposited material were correlated with changes in cooling rate during L-DED processing. The developed L-DED repair process for the damaged HPDC insert removes the heat checking crack and deposits material with micro-spot L-DED, restoring the component’s geometry. After the repair process, external and internal analyses provide valuable insights into the geometrical accuracy of the repair region, the microstructural and microhardness differences iii between the softer deposited material, the harder base material, and the traits of the heat-affected zones. This work showed that micro-spot L-DED is feasible for repair, but it also showed key areas in the repair methodology that require improvement before industrial implementation. Additionally, the unique response of weld beads and cuboid samples to process parameters warrants further investigation, focusing on the optimization of gas flow and powder feed rate settings for micro-spot L-DED systems.

Text

2024-09-16

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/89000

Mechanical Engineering

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/4.0/