Manufacturing of FeCoCrNiCux medium-entropy alloy coating using laser cladding technology

The FeCoCrNiCux medium-entropy alloy coatings were manufactured on Cr12MoV die steel by the laser cladding technology. Due to the dilution effect of the substrate, the content Fe element in the cladding layers was found to be enhanced obviously. The molar ratio of elements in the original high-entropy alloy powders was broken. The mixed entropy values of the four cladding layers, were calculated by the Boltzmann equation, belong to the medium-entropy alloy category. The atomic radius difference between the Cu and the other four elements were large. Hence, the Cu element was easy to segregate in the grain boundaries to form the Cu-rich solid solution. Furthermore, the Cu element could enhance the Gibbs free energy of the cladding layers. Thus, the segregation behavior of the Cu element became serious with the increase of its content. The potential difference between the Cu-rich solid solution and the metal matrix is large. Therefore, the segregation of the Cu element would deteriorate the corrosion resistance of the cladding layers. In the high-temperature oxidation test, the Cu element could promote the formation of the large oxides, which reduced the protection of the oxidation film to the cladding layer metal.308