Influence of B4C Content on the Properties and Microstructure of CoCrFeNiSi High-entropy Alloy (HEA) Coatings Laser Clad onto 45 Steel

Even though 45 steel is widely used in many industrial manufacturing fields, its properties of 45 steel sometimes cannot meet the requirements in special applications. In this study fibre laser cladding of 45 steel with CoCrFeNiSi high-entropy alloy (HEA) composite coatings reinforced with B4C was achieved with contents of 0, 4, 8, 12 and 16 wt.% mixed powders. The results showed that most B4C particles decomposed and reacted with Fe, Co, Cr and Ni atoms to form M7C3 and M2B (M=Co, Cr, Fe, Ni) under the irradiation of the laser beam. The HEA coatings were mainly comprised of M2B, M7C3 and BCC phases. The M2B appeared leaf-shaped and then changed into multiple parts with the increase of B4C content. When the content of B4C was 8 wt.%, the microhardness of the coating reaches its maximum (1430.5 HV0.3), and its friction coefficient is reduced by 36%. Proper B4C addition can effectively improve the surface properties of the coatings.