This study investigates the impact of carbon (C) doping on the phase and microstructure of CoCrFeNiTi0.5 high-entropy alloy (HEA) layers, aiming to enhance their microhardness and wear resistance. The addition of C improves the microhardness and wear resistance of the CoCrFeNiTi0.5Cx HEA layers. The layers are composed of a BCC solid solution (Fe-Cr-based), a Ti-rich phase, and TiC. Increasing the C content increases the lattice constant and lattice distortion of the BCC solid solution, leading to the segregation and formation of TiC. The microstructure of the CoCrFeNiTi0.5Cx layers exhibits a gradient change from equiaxed crystals to dendrites to columnar crystals. The increase in C content results in denser TiC between grains, refining the microstructure, which enhances microhardness and reduces frictional coefficient, friction track depth, and wear rate. The nucleation, growth, and precipitation behavior of the second phase in the CoCrFeNiTi0.5Cx layers are systematically studied, and the strengthening behavior is analyzed, focusing on precipitation and fine grain formation. The friction behavior, damage mechanism, and wear-resistant mechanism of the CoCrFeNiTi0.5Cx layers under different friction parameters are also revealed. The study provides a theoretical basis for the wear-resistant application of high-entropy alloy layers in engineering.This study investigates the impact of carbon (C) doping on the phase and microstructure of CoCrFeNiTi0.5 high-entropy alloy (HEA) layers, aiming to enhance their microhardness and wear resistance. The addition of C improves the microhardness and wear resistance of the CoCrFeNiTi0.5Cx HEA layers. The layers are composed of a BCC solid solution (Fe-Cr-based), a Ti-rich phase, and TiC. Increasing the C content increases the lattice constant and lattice distortion of the BCC solid solution, leading to the segregation and formation of TiC. The microstructure of the CoCrFeNiTi0.5Cx layers exhibits a gradient change from equiaxed crystals to dendrites to columnar crystals. The increase in C content results in denser TiC between grains, refining the microstructure, which enhances microhardness and reduces frictional coefficient, friction track depth, and wear rate. The nucleation, growth, and precipitation behavior of the second phase in the CoCrFeNiTi0.5Cx layers are systematically studied, and the strengthening behavior is analyzed, focusing on precipitation and fine grain formation. The friction behavior, damage mechanism, and wear-resistant mechanism of the CoCrFeNiTi0.5Cx layers under different friction parameters are also revealed. The study provides a theoretical basis for the wear-resistant application of high-entropy alloy layers in engineering.