Solution-Based Deposition of Anatase Nanoparticle Films for the Mechanical Reinforcement of Steel

The limited surface hardness of austenitic stainless steels such as SAE 304 often curtails their utility in applications requiring high mechanical durability. To address this, we report on a simple, low-temperature, solution-based method to significantly enhance the surface properties of this steel. Nanocrystalline titanium dioxide (TiO2) films were deposited on SAE 304 substrates via dip-coating from a colloidal suspension of oleate-capped anatase nanoparticles, followed by a non-thermal consolidation process. X-ray diffraction analysis of the resulting film confirmed the formation of a phase-pure anatase coating with an average crystallite size of 5.6 nm, demonstrating the preservation of the nanostructure. Instrumented nanoindentation tests revealed a transformative improvement in mechanical performance; the surface hardness increased by over 200%, from 2.8 GPa for the uncoated substrate to 8.5 GPa for the coated sample. These findings validate that a scalable, non-vacuum, low-temperature deposition route can produce mechanically robust ceramic coatings, presenting an economically attractive and effective pathway for the advanced surface engineering of metallic components.