Multi objective optimization of forming quality and wear resistance in cross-scale Nano / Micro -WC reinforced AlCoCrFeNi2.1 high entropy alloy composite coatings in laser cladding

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.