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

In the present research, FeCoCrNiCux medium-entropy alloy coatings were manufactured on Cr12MoV die steel by laser cladding technology. Due to the dilution effect of the substrate, the actual mixed entropy value of the coatings was found to be less than the theoretical value, indicating a typical medium-entropy alloy. The addition of Cu element was found to increase the Gibbs free energy of the cladding layers. Moreover, the difference in atomic radius between the Cu element and the other four elements is large. Thus, the Cu element segregates easily at the grain boundaries. The micro-hardness of the cladding layers was lower for the simple face-centered cubic structure, about 250 HV. Owing to the low hardness value, the wear mechanism of the cladding layers consisted of adhesive wear, abrasive wear, and oxidative wear. The Cu element segregated in the grain boundaries to form the Cu-rich solid solution. The large potential difference between the metal matrix and the Cu-rich solid solution deteriorated the corrosion resistance of the cladding layers. Furthermore, it was found that the addition of Cu element could lead to the formation of large oxides, thereby reducing the high-temperature oxidation resistances of the cladding layers. The surface layer of the oxidation film consisted of mainly Fe oxides while the internal layer consisted of Cr oxides. (C) 2017 Published by Elsevier Ltd.