Fracture and wear mechanisms of FeMnCrNiCo plus x(TiC) composite high-entropy alloy cladding layers

FeMnCrNiCo + x(TiC) composite high-entropy alloy (HEA) coatings were manufactured by laser cladding. Then the small punch and wear experiments at room temperature were conducted. The phases and microstructures of the composite HEA coatings were characterized using XRD, SEM/EDS, EBSD and TEM, and the strengthening, fracture and wear mechanisms of coatings were systematically analyzed and discussed. The results showed that small-sized particles and large-sized particles in coatings reduced the nucleation energy barrier of grain, and particles precipitated at grain boundaries hindered the movement of grain boundary. And the refined grain and increased dislocation density enhanced the capability of coatings to resist potential plastic deformation. As for the properties, the strength of the coating with 5 wt% TiC was increased, but cracks easily initiated and propagated around the precipitated particles at grain boundaries, which lowered the toughness. The excess TiC made the brittle and large-sized particles become cracking sources in coatings, thus the strength and toughness of coatings were deteriorated. Obvious fatigue wear tendency in these two coatings (5 wt% & 10 wt%) influenced their service life in the wear environment, although the coating with 10 wt% TiC had better surface wear performance.