Abstract
<title>Abstract</title> <p> Annealing is widely applied to reduce porosity and enhance the wear resistance of thermally sprayed metallic coatings; however, its effectiveness is often limited by grain coarsening and brittle phase formation. Here, we present a new approach that directly overcomes these limitations by coupling thermal spraying with the crystallization behavior of a rationally designed amorphous alloy powder (Ni <sub>68.6</sub> Cr <sub>8.7</sub> Nb <sub>3</sub> P <sub>16</sub> B <sub>3.2</sub> Si <sub>0.5</sub> ). Upon annealing at 800°C for 1 h, the metastable Mg <sub>6</sub> Cu <sub>17</sub> Si <sub>7</sub> -type phase present in the as-sprayed coating transforms into a well-refined three-phase microstructure, comprising a ductile Ni-based solid solution and hard Ni <sub>3</sub> P and NbNi <sub>3</sub> intermetallic phases, with 51% reduced intersplat density. This microstructural configuration results in a 21% reduction in COF and an 89% reduction in wear rate. The worn surface of annealed coating demonstrates minor thin grooves, lower fractions of oxides, and no sign of spallation, delamination or cracking, presenting a significant improvement in the wear resistance after annealing. This improvement originates from the three-phase composite microstructure in which the ductile Ni-based solid solution provides plastic deformability and crack resistance, whereas the hard Ni <sub>3</sub> P and NbNi <sub>3</sub> phases provide hardness and load-bearing capacity. Annealed coating exhibits mild abrasive wear mechanism coupled with limited plastic deformation. These findings demonstrate that controlled crystallization of thermally-sprayed coatings can be used to engineer beneficial phases, providing a promising strategy for the design of high-performance wear-resistant coatings. </p>