Optimized wear behaviors and related wear mechanisms of medium entropy alloy-based composite coatings

In this work, the (10 wt%, 30 wt%, 50 wt%) TiC reinforced AlFeCrCo medium entropy alloy (MEA) lightweight composite coatings with the extremely low porosity were successfully fabricated on Mg alloy substrate by resistance seam processing. The results showed that the microstructure of composite coating was consisting of a BCC-based MEA matrix and TiC particles, and a good metallurgical bonding with a semi-coherent relationship was formed between the coating and Mg alloy. Furthermore, the lightweight composite coatings (5.6–6.5 g cm−3) showed improved corrosion resistance over Mg alloy substrate. Specifically, the composite coatings exhibited optimized wear performance in the dry, deionized water and 3.5 wt% NaCl solution conditions with the increasing TiC content, surpassing related high/medium entropy alloy coatings, which is attributed to the formation of a coherent interface between the MEA matrix and the TiC particles. The first-principles calculations were performed to elucidate the nature for the higher bonding strength of TiC/MEA interface. In these wear conditions, the main wear mechanisms of composite coatings were discussed in terms of adhesive wear, oxidative wear and/or corrosive wear, in connection with their microstructure features and electrochemical behaviors. Based on the elevated anti-corrosion ability, this work has provided a strategy to fabricate advanced coatings on Mg alloys endowing with lower density, interfacial metallurgical bonding and optimized wear resistance, substantially contributing to the development of high-performance composite coatings.