Microstructure and tribological performances of Cr3C2- and B4C-added CoCrFeNiMo HEA coatings prepared by laser cladding

The inadequate wear durability of CoCrFeNiMo high-entropy alloy coatings poses great challenges to achieving reliable surface protection for engineering components. This study strategically addresses this limitation by incorporating ceramic carbide particles. The pure CoCrFeNiMo (P0), CoCrFeNiMo-10wt%Cr₃C₂ (CrC10), and CoCrFeNiMo-10wt%B₄C (BC10) composite coatings were deposited onto Q235 substrate utilizing laser cladding. Those coatings' structural characteristics, mechanical properties, tribological behavior, and wear mechanisms were analyzed and compared. The P0 coating was composed of FCC and σ phases with a herringbone-like hierarchical eutectic structure, showing good fracture toughness (10.7–24.61 MPa·m^1/2). The Cr₃C₂-added coating had a typical dendrite structure, and the primary phase from FCC gradually transformed upward into the σ phase. Adding B₄C particles induced plenty of carbides and borides precipitation such as MoC, M₇C₃, and Fe₃(B, C) in BC10 coating. Adding carbide particles promoted the solid solution strengthening of C and B atoms and in-situ precipitation of reinforcement phases, significantly enhancing the hardness. The hardnesses of P0, CrC10, and BC10 coatings were 652.8, 744.3, and 1162.1 HV_0.2, respectively. Benefiting from the synergistic effect of the Mo-rich hardening phase and lubricating oxide layer, the BC10 coating achieved the lowest wear rate (9.8 × 10⁻⁶ mm³·N⁻¹·m⁻¹), showing an order-of-magnitude improvement over the P0 and CrC10 coatings. The P0 and CrC10 coatings predominantly exhibited abrasive wear modes. Surprisingly, the worn surface of the BC10 coating was very slight without detectable scratches or delamination, which was dominated by oxidative wear.