A Statistical Prediction of Multiple Responses Using Overlaid Contour Plot on Hydroxyapatite Coated Magnesium via Cold Spray Deposition

This work aimed to search optimal values for the properties of hydroxyapatite coated pure magnesium produced by cold spray deposition. Using fractional factorial design (2k-1), standoff distance, surface roughness and substrate heating temperature during cold spraying were selected as significant factors while number of sprays as insignificant factor. The responses chosen are coating thickness, hardness and elastic modulus of the coating. The analysis of the contour plots for thickness revealed that high thickness (>40 μm) was obtained when standoff distance is at 20-25 mm, surface roughness at 240-700 grit and substrate heating temperature at 350-550 °C. High nanohardness (>400 MPa) obtained when standoff distance is at 20-35 mm, surface roughness at 240-900grit and substrate heating temperature at 350-550 °C. High elastic modulus (>40 GPa) was obtained at 20-30 mm for standoff distance, 240-800 grit for surface roughness and 350-550 °C for substrate heating temperature. The contour plot of coating thickness, nanohardness and elastic modulus were overlaid to find the feasible region.