Structural, tribological, and corrosion properties of Cr₃C₂-NiCr coatings obtained by the HVOF technique

This work focuses on improving the operational durability of 12Kh1MF steel boiler tubes employed in thermal power engineering. Cr₃C₂–NiCr protective layers were produced by High Velocity Oxy-Fuel (HVOF) thermal spraying, followed by a comprehensive evaluation of their phase composition, mechanical behavior, tribological response, and corrosion resistance. The results demonstrated that substrate preheating at various temperatures (room temperature, 100 °C, and 200 °C) had a pronounced influence on the coating structure and performance. SEM observations showed that the formed coatings had a dense microstructure with reduced porosity. XRD analysis verified the phase stability of Cr₃C₂ and confirmed the role of the NiCr binder in securely anchoring carbide particles, which limits coating degradation at elevated temperatures. Among the investigated conditions, preheating at 100 °C provided the most favorable combination of properties, including enhanced hardness (up to 897.8 HV), lower surface roughness, stabilized friction behavior, and a minimum wear track diameter of 712 μm. Furthermore, a noticeable decrease in corrosion rate was observed. These findings indicate that Cr₃C₂–NiCr coatings fabricated by HVOF spraying can serve as reliable protective layers for components operating under severe high-temperature conditions.