Experimental Investigation and RSM Optimization of Nd:YAG laser Processing Parameters for Sol-Gel Deposited Hydroxyapatite-Titanium dioxide Coated SS 316L stainless steel

The research focuses on Response Surface Methodology (RSM) to optimise process parameters for HA-TiO2 nanocomposite coatings on SS 316L substrates, organised using the sol-gel method and modified with Nd:YAG laser surface treatment. Four process variables (cutting speed, nozzle height, peak power and duty cycle) was carefully adjusted using RSM to determine their impact on surface roughness (Ra), heat impacted zone (HAZ) and kerf deviation. A central composite design with 30 experimental trials was used to create credible predictive models and examine parameter interactions. The results find that higher laser power and duty cycle (%) with lower scan speeds leads to higher Ra and thicker coatings, while moderate laser energy with optimal scan speed generates smoother, more uniform and adherent coatings.The measured Ra levels varied from 18.50 μm to 29.77 μm, with lower roughness at higher scan speeds and reduced power and higher roughness at low scan speeds and increased power. Heat-affected zone (HAZ) ranged from 0.573 mm to 2.204 mm and kerf deviation ranged from 0.355 mm to 0.841 mmwhich increased with larger thermal input. The optimised lasersol-gel parameters improve the useful, structural and tribological properties of HA-TiO2- coated SS 316L surfaces which show them suitable for biomedical implant applications.