<p>This paper explores the nano-reinforced Cr₃C₂ composite coating developed on the ASTM-SA213-T91 boiler tube steel by the use of high-velocity oxy-fuel (HVOF) thermal spray technique, and the dependency between microstructural characteristics and the mechanical performance of these coatings is correlated. The basic Cr₃C₂ coating was altered by incorporating nano-Y₂O₃ and nano-SiC reinforcement to strengthen the densification of the coating and surface integrity. The ensuing coatings were systematically characterized based on microhardness, porosity, and micrographic features, whereas phase constitution and elemental distribution were studied through scanning electron microscopy (SEM), x-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), and elemental mapping. The introduction of nano-scale reinforcements caused a significant decrease in porosity and a significant increase in hardness, which guarantees a better splat bonding and coating compactness. Microstructural examination proved the homogeneous distribution and chemical stability of the nano-additives in the Cr₃C₂ matrix designed in the high-temperature spraying. Since little has been documented on nano-Y₂O₃ and nano-SiC-reinforced Cr₃C₂ coating generated by HVOF on the T91 steel, the current research yields new information on coating design strategies to boost the service life and performance of the boiler component in severe thermal and corrosive conditions.</p>