Amorphous alloy reinforced Cu-based immiscible coatings by laser melting deposition: Separation mechanism and corrosion behavior

Abstract

In order to clarify the effect of Fe-based amorphous alloy on the separation mechanism and corrosion behavior of Cu-based immiscible coatings, 10 wt% Fe-based amorphous powder was designed into 90 wt% pure Cu powder to produce the amorphous alloy reinforced Cu-based immiscible coatings by laser melting deposition. The self-organized microstructure and corrosion behavior of immiscible coatings with different laser energy densities were investigated. When the different laser energy densities are adopted, many carbides (M23C6 and M12C) are dispersed in the lower α-Fe layer and large amounts of α-Fe particles containing carbides are embedded in the upper ε-Cu layer due to liquid phase separation. With increasing laser energy density (LED), the α-Fe dendrites are coarser and the area of carbides decrease. The interface of coating and substrate experiences a transition from “poor bonding (gaps) to “good bonding” and “crack debonding”. Moreover, the corrosion characteristics of immiscible coatings also experience a transformation from “crevice corrosion” to “enhanced protection of passive films” and “reduced protection of passive films”. As a result, the corrosion resistance increases first then decreases and the immiscible coating deposited by the LED of 31.25 J/mm2 exhibits the highest corrosion resistance.