Effect of V addition on the microstructure and wear resistance of CoCrFeNiNb high-entropy alloy laser cladding layers

In this study, CoCrFeNiNbVx (x = 0, 0.5, 1, 1.5) high-entropy alloy (HEA) laser cladding layers were fabricated to investigate the effects of V content on the microstructure evolution, as well as room-temperature and high- temperature wear resistance of the cladding layers. It was found that all cladding layers exhibited a typical hypereutectic morphology. With increasing x, the stability of the FCC phase decreased, gradually transitioning from FCC phase + Laves phase (primary Laves phase + secondary Laves phase) + NbC to BCC phase + Laves phase (primary Laves phase + secondary Laves phase). At x = 1, the primary Laves phase accounted for 41.6 % of the structure and exhibited optimal size uniformity. Compared to DT4 industrial pure iron, the microhardness of the cladding layers was significantly improved, which can be attributed to the combined effects of second-phase strengthening, solid solution strengthening and dispersion strengthening. As x increased, the microhardness, room-temperature wear resistance, and high-temperature wear resistance of the cladding layers initially increased and then decreased, reaching optimal values at x = 1, where they were 1.61, 7.04, and 7.40 times higher than those at x = 0, respectively. The improvement in room-temperature wear resistance can be attributed to the increased Laves phase content and the formation of Fe-, V-, and Nb-enriched oxide layers. The enhancement in high-temperature wear resistance is due to the increased Laves phase content and the lubricating effect of VxOy. The addition of V significantly improves the properties of high-entropy alloys and provides an effective approach for preparing cladding layers with good wear resistance and high-temperature wear resistance.