The aerospace industry wishes to investigate the possibilities of additive manufacturing (AM) processes to produce parts with improved design flexibility in cost-effective and environmentally friendly ways, serving as a complement to today's conventional manufacturing methods. MERLIN is an EU-funded research project constituting of University West and GKN Aerospace Sweden AB among others, with focus on developing AM for productivity improvements, monitoring and control techniques as well as thermal management strategies.

The aim of this thesis work was to investigate the possibilities to build up a defined deposit geometry of Alloy 718 filler material onto flat Alloy 718 substrate plates by using the robotized laser metal wire deposition (rLMD-w) process. Alloy 718 belongs to the superalloys, a metal group that have been commonly used in aircraft engine and gas turbine applications due to their excellent material properties at elevated temperatures. The focus of the thesis was directed towards investigating the process stability and deposited material quality. A set of iterative experimental process trials combined with metallographic evaluations were conducted at the facilities of Production Technology Centre (PTC), in close collaboration with GKN Aerospace Sweden AB.

The results revealed that both the deposition process and the microstructure are favored by maintaining a low delta-temperature throughout the welding build-up. Two thermal management strategies were applied, with their combined use showing to have the most beneficial outcome to the deposit quality. The delta-temperature effect is believed to have connections to hot cracking mechanisms and the relative cracking susceptibility of superalloys.

The work conducted within this thesis was not able to succeed in building a deposit completely free from material defects. The final experiment geometry was however greatly improved regarding smooth and repeatable material transfer, with only minor online adjustments being necessary by the operator. The material defects in the form of lack of fusion and cracks were also immensely decreased in both size and quantity, compared to initial trials. The last deposit built, incorporating both thermal management strategies, resulted in no lack of fusion defects and only one micro-sized crack of 363 μm found between the top two layers of the geometry (layer 9 and 10).