Microstructure and tribological properties of in-situ MxB reinforced CoCrFeNi HEA composites prepared by laser cladding

Abstract

The CoCrFeNiTixB2x (x = 0, 0.1, 0.2, and 0.3) high entropy alloy (HEA) composite coatings were prepared on Q235 substrates by laser cladding. The microstructure, grain orientation, precipitated phase and tribological properties of the coatings were investigated by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), X-ray diffraction (XRD), transmission electron microscopy (TEM) and high-speed reciprocating wear friction tester, respectively. The results show that TiB, Cr2B, FeCrB and (FeCr)2B phases were in-situ formed in the composite coatings. The microstructures of the coatings are refined and the hardness increases with the addition of Ti and B elements. The grain orientation of all coatings is random. The orientation relationships between the HEA matrix and Cr2B is HEA matrix (002) // Cr2B (1̅3̅1̅), HEA matrix [5̅10] // Cr2B [013̅]. The composite coating exhibits the best wear resistance when the x of CoCrFeNiTixB2x is 0.2. The primary strengthening mechanisms of Ti and B doped CoCrFeNi HEAs are the synergistic effect of solid solution strengthening, second phase strengthening and fine grain strengthening.