<p>Steam turbine valve stems are subjected to the coupled effects of high-temperature oxidation, thermal fatigue stress, and high-temperature wear during start-stop cycles and long-term service, which severely restricts their service reliability and service life. To achieve efficient surface strengthening and performance improvement of valve stems, in this study, nano-TiO₂-reinforced cobalt-based alloy composite coatings were fabricated on GH901 high-temperature superalloy substrates via laser cladding, and the influence laws of the modified coatings on microstructural evolution, microhardness, and high-temperature tribological properties were systematically investigated. The results show that the introduction of nano-TiO₂ can effectively regulate the microstructure and mechanical properties of the coatings and significantly refine the coating grains. The maximum microhardness of the coatings is increased by 39.1% compared with the substrate, and the maximum reduction in wear rate reaches 76.48%. This is attributed to the fact that the addition of nano-TiO₂ promotes the formation of a continuous and dense high-temperature oxide film on the coating surface, while the second-phase particles can effectively bear the friction load and exert a synergistic strengthening effect. This study confirms that optimizing the content of nano-TiO₂ to regulate the coating microstructure can achieve the synergy of multiple strengthening mechanisms, significantly improve the microhardness and high-temperature wear resistance of the coatings, and can provide feasible technical support and theoretical basis for the surface strengthening modification of key high-temperature alloy components.</p>