Effect of B/Si ratio on structure and properties of high-entropy glassy Fe25Co25Ni25(BxSi1-x)25 coating prepared by laser cladding

Abstract

The effects of the B/Si ratio on the glass formation, structure and properties evolutions for the high-entropy Fe25Co25Ni25(BxSi1-x)25 (x = 0.5, 0.6, 0.7, 0.8) coatings were investigated. The crack-free high-entropy glassy coatings were synthesized by using the optimized three-step broadband laser cladding process. The microstructure of the coatings consists of face-centered cubic (FCC), (Fe, Co, Ni)2B and amorphous phases for 0.5 ≤ x ≤ 0.6. Further the increase of the B/Si ratio (0.7 ≤ x ≤ 0.8), it promotes new tiny precipitation of (Fe, Co, Ni)3B phase. The average crystalline size and volume fraction of interdendrite regions are depending on B content. The variations in the mechanical properties of the coatings correspond to its structural evolutions. The hardness increases almost linearly from 5.24 GPa of the Fe25Co25Ni25(B0.5Si0.5)25 coating to 8.39 GPa of the Fe25Co25Ni25(B0.8Si0.2)25 coating. The wear resistance is also proportional to the x content. The mechanisms of the glass formation ability and the relationships between structure and properties of the present coatings were discussed. This combination of these excellent properties gives the new high-entropy glassy coating good prospect for the potential engineering applications.