Laser-Clad AlCoCrFeNiTi HEA Coating with In-Situ Al2O3@TiC Core–Shell Particles

Laser cladding was employed to deposit an AlCoCrFeNiTi high-entropy alloy coating on 45 steel substrate to enhance its surface properties. The coating microstructure consists of a BCC solid-solution matrix with B2-ordered precipitates and in-situ Al2O3@TiC core–shell nanoparticles. HRTEM reveals a semi-coherent interface between the core and shell, attributed to a low lattice mismatch of 6.43%. Mechanical and tribological tests show that the coating exhibits an average microhardness of 781 HV0.2, about 2.3 times that of the substrate, and a 31.25% lower friction coefficient and a wear rate only 57.75% of that of the substrate. The coating primarily undergoes abrasive wear, whereas the substrate suffers severe adhesive and oxidative wear. Strengthening originates from solid-solution and second-phase strengthening, with the hard Al2O3@TiC phase contributing to stability, hardness, and wear resistance. These results indicate that the core–shell structured coating effectively improves the surface performance of 45 steel and offers theoretical guidance for fabricating high-entropy alloy tool coatings via laser cladding.