Experimental and DFT studies on corrosion behaviors of laser-cladded (FeCoNi)75-xCrxB15Si10 high-entropy alloy coatings

The effects of Cr doping on microstructure evolutions and corrosion behaviors of laser-cladded (FeCoNi)75-xCrxB15Si10 (denoted as Crx hereafter, x = 0, 4, 8, 12, 16 at%) high-entropy alloy coatings (HEACs) were investigated. The composition and shape of the borides in interdendrite regions are modified by adding Cr, alleviating the localized corrosion behavior. The corrosion resistance of the HEACs increases continuously as a function of Cr level in 3.5 wt% NaCl solution. The Cr16 coating outperforms the previously reported Ni alloys, stainless steel, and some other high entropy alloys in terms of corrosion resistance, with the highest pitting potential (0.233 V), the lowest corrosion current density value of 9.9 x 10-9 A/cm2 and passive current density (2.138 x10- 8 A/cm2). Based on the experimental analysis and density functional theory (DFT) simulations, the corrosion mechanisms of the Crx HEACs were discussed. The exceptional corrosion resistance of the Cr16 coating can be attributed to its high oxygen adsorption energy and thus facilitates the rapid formation of protective and compact passive films with few defects.