Synthesis of TiAlN based coating on mild steel substrate using combined laser/sol-gel technique

In this work a novel method for synthesising a titanium aluminium nitride (TiAlN) based coating is reported. This was achieved by scanning a high-power diode laser over the surface of slurry of aluminium hydroxide and titanium hydroxide sol-gels, urea and graphite, which was uniformly spread over a mild steel substrate. The laser processing parameters giving rise to thermal conditions suitable for the synthesis of the coating were chosen through predictions from chemical thermodynamics analysis and computational fluid dynamics (CFD) modelling. The surface morphology and microstructure of the synthesised coatings were examined using optical microscopy, scanning electron microscopy and X-ray diffraction. The analyses revealed the formation of an inter-layer in the coating/substrate interface. This inter-layer is an indication that metallurgical diffusion took place across the coating/substrate interface and suggests an enhancement in coating/substrate interface bonding. The investigation demonstrated the potential of the laser/sol-gel process to deposit coatings with super-adhesive properties and good hardness and surface finish.