The surface quality of laminar cooling rolls directly affects the final quality of steel strips produced in continuous casting and hot rolling lines. In this study, Fe-Cr-Ni-Mo-B wear-resistant cladding layers with different Cr and B contents were fabricated on the surface of laminar cooling rolls by flux-cored arc welding (FCAW). The effects of alloy composition on microstructural evolution, carbides and borides morphology, and wear behavior of the cladding layers were systematically investigated, and the relationship between microstructural transformation and wear mechanisms was clarified. Increasing the B content from 0.3 wt.% to 0.6 wt.% promoted boride nucleation during solidification, resulting in the transformation of eutectic M₂B from coarse discrete particles into a fine continuous network structure. Meanwhile, grain refinement and increased dislocation density were achieved which enhanced hardness and load-bearing capability of the cladding layers, and the microhardness increased from 790.8 HV_0.1 to 852.4 HV_0.1. With a constant B content, increasing the Cr content from 15 wt.% to 19 wt.% accelerated the growth and coarsening of eutectic hard phases, inducing a morphological transition from a fine interconnected network to coarse skeletal and plate-like structures. Meanwhile, the increased Cr content promoted austenite retention, which reduced the microhardness of the cladding layers to 701.7 HV_0.1. Among all investigated samples, the Fe-15Cr-0.6B-2Ni-2Mo cladding layer exhibited superior wear resistance, which is mainly attributed to the formation of an effective load-bearing framework composed of fine continuous eutectic borides and the martensitic matrix. During high-temperature wear, this microstructural configuration effectively suppresses plastic deformation of the matrix and spalling of hard phases. Meanwhile, the oxide tribofilm formed on the worn surface reduces direct contact between the cladding layer and the counterface, thereby mitigating adhesive wear and material spalling. This study provides a new solution for surface strengthening of laminar cooling rolls.

Fe-Cr-Ni-Mo-B alloy,Flux-cored arc welding,Microstructure,Wear resistance