Strengthening mechanisms of laser cladding TiC/FeCoCrNiCu high-entropy composite coatings: Microstructure evolution and wear behaviors

The HEA-TiC high-entropy composite coatings with TiC (5, 10, 15 and 20 wt%) reinforced FeCoCrNiCu matrix were fabricated by laser cladding to investigate their tribological performances and wear behaviors at RT and 600 degrees C. As the percentage of TiC particles elevated, the microhardness was progressively enhanced to 531.65 HV 0.5 and its surface energy weakened to 24.29 mN/m. Whereas the excess TiC particles added into the coating internally appeared serious agglomeration, resulting in performance rebound. Fine-grain strengthening of high melting point and high hardness TiC acting as a heterogeneous nucleation site, precipitation strengthening of the Laves phase and dispersion strengthening of re-solidified carbides, and the blocking effect of TiC particles on dislocation motion. These reinforcing behaviors synergize to confer the desired tribological properties on the 15 wt% TiC coating, with outstanding wear resistance (7.6 x 10-6 mm3/N & sdot;m) at RT. The highly dense oxide film composed of TiO2 and the friction film reconstituted by Cr2O3 act synergistically on the coating surface at 600 degrees C, the wear rate guided by oxidative wear is reduced by 88.7 %, compared to the TiC-free coating.