Evolution in microstructure, properties of the laser cladding CoCrFeMoNi coatings at different annealing temperatures

Laser-cladding CoCrFeMoNi high-entropy alloy coating is composed of face-centred cubic, σ and µ phases. After annealing at 700 °C, many needle-like precipitates of the σ phase are found in the FCC solid solution, and the granular µ phase precipitated at the edge of the primary net-structural σ phase. After annealing at 800 °C, granular µ phases are found inside the primary σ phase. The friction coefficients of the coatings (as-cladded, as-annealed at 700 °C and 800 °C) decrease dramatically compared with the substrate of H13 steel. Obvious spheroidising of the σ phase at 900 °C leads to a decrease of hardness and an increase of friction coefficient. Furthermore, the CoCrFeMoNi high-entropy coatings show better corrosion resistance than H13 steel in 3.5 wt-% NaCl solution.