Effects of Fe-to-Co ratio on microstructure and mechanical properties of laser cladded FeCoCrBNiSi high-entropy alloy coatings

Abstract Effects of Fe-to-Co concentration ratio upon the glass forming ability (GFA) of the cladding powders had been quantitatively evaluated with theories applied in bulk amorphous materials, based on which laser cladded amorphous matrix composite coatings were successfully fabricated with FeCoCrBNiSi high-entropy alloy powders. The relationship between predicted GFA, amorphous phase content and wear resistance behaviors of the coatings had been investigated. The microstructure of the coatings was uniformly composed of amorphous phase, nano-crystalline β-Co phase, γ(Fe, Ni) and Co2B crystalline phases. Coatings obtained with the lowest Fe-to-Co ratio of about 1: 1 exhibited the highest amorphous content of over 66.7%, the highest microhardness and the most outstanding high-temperature wear resistance. Amorphous phase had optimized the wear mechanism which was a combination of abrasive wear and oxidation wear, and consequently improved wear resistance of the coatings. Increment in Fe-to-Co ratio weakened the GFA of the cladding powders and led to lower content of amorphous phase, which gave birth to lower microhardness, higher fraction of oxidation wear and thus higher wear rate of the coatings. The content of amorphous phase in the coatings was proved by the present research to be a novel and reasonable criterion for GFA evaluation of cladding materials.