Effect of B4C content on microstructure and properties of AlCoCrFeNi coatings by laser cladding

In order to enhance the mechanical properties of high-entropy alloy coatings, AlCoCrFeNi + x % B4C (x = 0, 5, 10, 15) composite coatings were prepared on the surface of H13 steel using laser cladding (LC) technology. The hardness of coatings was evaluated using a micro-Vickers tester. Electrochemical corrosion behavior of coatings was studied by using electrochemical technique. Additionally, friction and wear tests were conducted to evaluate the tribological performance of the coatings. The results show that the precipitated phases are M7C3 (M = Cr, Fe), Fe2B, and CrB. The hardness of B15 reaches 1063HV0.5, and the hardness of the coating is increased by 89%. With the increase in B4C content, the dense reticular phase changes into a large needle-like phase. The precipitated volume fraction continuously increases with the increase in B4C content. Therefore, the improvement in the coating hardness is primarily attributed to the precipitated phase. Additionally, the increased of lattice distortion, elevated dislocation density, and reduced of grain size collectively contribute to the improved properties of the coating. Grain refinement and dense reticular phase can resist the corrosion of electrolytes to the metal interior and improve the corrosion resistance of the coating. However, the large precipitated phase and the rise in dislocation density lead to the deterioration of corrosion resistance. Under the applied load, the large precipitated phase is broken and separated from the matrix, subsequently acting as abrasive particles during the wear process. The wear form of the coating is abrasive wear.