Laser Metal Deposition of Aluminium-Copper alloys for Repair applications

Overview & Synopsis

The present thesis aims at demonstrating the feasibility of repairing high performance castings made of an aluminiumcopper alloy using the Laser Metal Deposition metal additive manufacturing process. These alloys present a low weldability and thus cannot be reliably repaired with manual arc-welding processes. To instead use this innovative additive manufacturing process for repair applications and thereby improve upon current methods, major challenges had to be overcome regarding the flowability and solidification behavior of this aluminium alloy powder as well as the overall methodology to reliably and efficiently perform the repair operation. Experimental, theoretical and numerical studies allowed to elucidate some of these aspects and eventually enabled the use of a 224.0 casting aluminium alloy with the Laser Metal Deposition metal additive manufacturing process. A repair methodology including a robust segmentation algorithm was also developped to automate the repair process and permit the generation of toolpaths based on raw in-situ 3D scanning measurements. Repairs of high performance aluminium-copper castings were carried out successfully as no major lack of fusion, bonding or cracking defects were observed. A metallographic analysis showed that the aluminium deposits obtained by Laser Metal Deposition generally offer a refined microstructure with limited solute segregation and hot cracking.