Development of CoCr0.65FeNi-BSiC as a self-fluxing high-entropy alloy for thermal spraying

Abstract

Self-fluxing alloys are used as thermal spray coatings for superimposed tribological and corrosive stresses. Subsequent fusing of self-fluxing alloy coatings forms a gas- and liquid-tight and strongly adherent coating. These alloys have been generally composed of one property defining main element and minor alloying elements such as Cr, Si, B and C. However, high-entropy alloys (HEAs) promise a significant improvement of the coating properties by solid solution strengthening and allow fulfilling increased application requirements. The current study focuses on the development of a self-fluxing HEA for thermal spraying using a novel CoCr0.65FeNi matrix with the alloy constituents B, Si and C. The CoCr0.65FeNi-BSiC powder was produced by gas atomization. Bulk material was produced in an arc furnace and by spark plasma sintering as a reference condition. The coatings were deposited using powder flame spraying. After fusing, the coating exhibits a closed porosity and good metallurgical bonding. The microstructure, phase formation, and wear behavior of the thermally sprayed CoCr0.65FeNi-BSiC self-fluxing HEA system in conjunction with the commercially available alloy Ni600 were analyzed. The fused CoCr0.65FeNi-BSiC coating exhibited a similarly high sliding wear resistance as the fused Ni600 coating. The high wear resistance and formation of a dense coating confirm the potential of this new development approach.