Effects of flame spray coating of Al₂O₃–TiO₂ on the structural and mechanical properties of boron steel surfaces

Abstract In this study, a boron-alloyed microalloyed steel was subjected to austenitizing and tempering heat treatments, followed by surface coating using the flame spray technique. Ceramic powders containing 87% Al₂O₃ and 13% TiO₂ with an average particle size of approximately 50 μm were used to produce coatings at three different thicknesses. Prior to coating, surface preparation was performed by sandblasting treatment to ensure optimal adhesion. After the coating process, the density of the coatings was measured using the Archimedes principle to indirectly assess porosity, interfacial bonding quality, and overall coating integrity. The phase structure, crystallinity, and structural transformations of the coated surfaces were analyzed by X-ray diffraction (XRD). Additionally, dislocation density values were calculated from the XRD data to evaluate the crystallographic characteristics of the coatings. The mechanical performance was assessed through wear tests and hardness measurements conducted on both coated and uncoated samples. The results demonstrated that the flame spray coating significantly enhanced the surface properties of the boron-alloyed steel, providing up to a 45% improvement in wear resistance. Furthermore, salt spray corrosion testing revealed that the coated specimens exhibited superior corrosion resistance without any visible surface degradation, highlighting the effective environmental protection offered by the Al₂O₃–TiO₂ ceramic coating.