Influence of process parameters on the properties of AlCoCr2FeMo0.5Ni high-entropy alloy coatings produced with laser directed energy deposition

Aerospace industry is constantly seeking new advanced materials with high-temperature properties. Since turbine engines are subject to arduous operating conditions, the alloys used for this application are required to exhibit high fatigue, creep, oxidation, and corrosion resistances. The emerging high-entropy alloys (HEAs) show a positive potential for replacing nickel superalloys in turbine components. High-entropy alloys are composed by five or more principal elements, which generate simple crystal structures—mostly body-centered cubic (BCC) and face-centered cubic (FCC) —that are stable at elevated temperatures. High-entropy alloy fabrication typically employs traditional methods, which impose strong limitations in geometric freedom and microstructure control. Additive manufacturing represents a promising alternative, since it allows us to overcome some of the drawbacks associated with subtractive technologies. In this research, AlCoCr2FeMo0.5Ni high-entropy alloy was processed using laser directed energy deposition technology with the aim of achieving a homogeneous deposition, free of defects, and well adherent to the substrate. Single-track and multitrack tests were carried out with different combinations of laser power, scanning speed, and powder feed rate. A preliminary evaluation of the results using an optical microscope revealed a correlation between the defects and the process parameters, enabling the identification of the optimal print setup. An in-depth analysis at a scanning electron microscope was performed to assess the microstructure and distribution of alloying elements. Additionally, microhardness tests were carried out to confirm the uniformity of phases within the deposition. Finally, the analysis of deposition morphology yielded three-dimensional maps and surface roughness values.