Microstructure and tribological properties of Y2O3-doped Fe-based alloy coatings by laser cladding

The laser-clad Fe45 alloy coating inherently comprises multiple crystalline phases, resulting in a heterogeneous microstructural distribution that influences its performance. In this study, the rare earth yttria (Y2O3) was employed to modify laser-clad Fe45 alloy coatings, and the effects of Y2O3 addition on their microstructure, microhardness, and tribological properties were investigated. As the Y2O3 content increases from 0% to 0.3wt.%, the dominant microstructure transforms from columnar crystals to fine cellular and equiaxed crystals. The modified coating with 0.3wt.% Y2O3 achieves a surface hardness of 568 HV0.3 and a wear volume of 1,735.41 µm3, representing a 14.06% increase in hardness and a 51.16% reduction in wear volume compared to the undoped coating. Further increasing the Y2O3 content from 0.3wt.% to 0.9wt.% gradually leads to the emergence of a coarser feather-like microstructure, characterized by a dendritic framework with inter-dendritic equiaxed crystals. Concurrently, both the hardness and wear resistance of the coating decrease. Nevertheless, all Y2O3-modified coatings surpass the undoped Fe45 coating in both hardness and wear resistance. Appropriate Y2O3 doping effectively refines the Fe45 alloy coating’s microstructure and induces lattice distortion, thereby enhancing its hardness and wear resistance.