Response Surface Methodology-based Optimization of Laser Cladding Parameters for Hardness of AlTiSiCrCo coated Ti6Al4V

This study investigates the optimization of laser cladding parameters to enhance the surface hardness of Ti6Al4V using an equiatomic AlTiSiCrCo high entropy alloy (HEA) coating. Although Ti6Al4V exhibits superior mechanical properties and corrosion resistance, its relatively low hardness limits its application in various industries such as aerospace, chemical, and biomedical. To address this limitation, response surface methodology (RSM) with a central composite design (CCD) was employed to investigate the effects of laser power (0.6-1.0 kW) and scan speed (0.3-1.2 m/min) on the surface hardness. Laser cladding was performed using a 3-kW fiber laser system, and microhardness measurements were conducted on cross-sectioned samples to evaluate the response. The results showed that the highest hardness of 840.87 HV at 0.8 kW and 0.3 m/min occurred at extreme conditions but were filled with cracks and pores. In contrast, the parameter combination of 0.8 kW and 0.75 m/min achieved an optimum hardness of 533.23 HV with a defect-free microstructure. This study focused on hardness and macrostructural observations (cracks and pores), crystallographic analysis was outside of the scope of the study. This condition presented the best combination of hardness and coating integrity. ANOVA confirmed the model significance (R 2 =0.9537, adjusted R 2 =0.9207). Although the predicted R 2 (0.6709) was lower, the experiments validated the predictive capability of the model. This study showed that RSM is effective for identifying the processing window of laser cladding HEA, where optimum must be a balance between hardness properties and defect and crack free coat. Keywords: Laser cladding, Ti6Al4V, High entropy alloy, Optimization, Response surface methodology, hardness