AlCoCrFeNi 2.1 high-entropy alloy composite coatings reinforced with micro/nano-sized tungsten carbide (WC) particles were fabricated via laser cladding in this study, to address the limitations of single-dimensional reinforcement strategies and optimize the wear resistance, microhardness, and porosity of the coatings. Three WC particle sizes, namely nano-WC, micro8-WC, and micro40-WC, were incorporated into the matrix to explore the influence of particle size and distribution on the microstructure and wear mechanisms. Though multi-objective optimization using simplex centroid mixture design, the optimal WC ratio was determined to be 9.5 wt% Nano-WC, 13 wt% Micro8-WC, and 7.5 wt% Micro40-WC. The AlCoCrFeNi 2.1 /WC composite coating achieved the best combination of low porosity, high microhardness, and superior wear resistance, with a volume wear rate as low as 8.34 × 10 −5 mm 3 /(N·m), demonstrating significant improvement compared to individual nano- and micro-WC coatings. Microstructure analysis revealed that the cross-scale WC particles synergistically induce significant lattice distortion, grain refinement, and the formation of strengthening phases such as Fe 3 W 3 C, Cr 7 C 3 , and WAl 12 . The presence of nanotwins within the WAl 12 phase contributed to both strengthening and toughening. The dominant wear mechanism shifts from adhesive wear in the nano-WC coating and oxidation coupled with abrasive wear in the micro-WC coating to primarily oxidative wear in the optimized dual-scale WC coating. This study provides valuable insights into the optimization of cross-scale particle-reinforced coatings, offering a path to achieving coatings with enhanced mechanical properties and wear resistance for complex service conditions. • Employ multi-objective optimization methods to systematically design experiments aimed at identifying the optimal material composition, balancing competing performance criteria through iterative modeling and validation. • Research has been conducted to explore the synergistic mechanism between micron and nano WC particles, demonstrating how their multi-scale collaboration improves key properties such as hardness, porosity, and wear resistance. • The transition in wear mechanisms has been verified through comprehensive microstructural characterization, employing techniques such as SEM, TEM, and EDS to correlate morphological and compositional changes with evolving wear behavior.
Zhang et al. (Wed,) studied this question.