Hydroxyapatite coating processes with electrophoretic deposition method on cobalt based alloys produced by selective laser melting and examination of the surface properties of the coatings

In recent years, the design and fabrication of patient-specific implants have gained increasing importance in biomedical applications. In this context, additive manufacturing technologies have played a critical role, particularly in enabling the production of complex geometries and patient-specific structures. To enhance the biocompatibility and surface characteristics of metal-based materials commonly used in orthopedic and dental implants, various ceramic coating techniques have been developed. In this study, hydroxyapatite (HA) coatings were applied onto the surfaces of CoCrWMo alloy specimens fabricated by selective laser melting (SLM), using the electrophoretic deposition (EPD) method, in order to investigate their effect on biomaterial performance. Prior to coating, a sandblasting process was performed using glass particles in the size range of 250–500 µm to increase surface roughness and improve the adhesion strength of the coating. The coating suspension was prepared by dispersing 0.25 g of HA powder into 50 mL of butanol. The EPD process was conducted at applied voltages of 200 V, 250 V, and 300 V, with a constant deposition time of 60 seconds for all samples. After coating, the microstructure, elemental composition, and phase content of the coated surfaces were analyzed using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD), respectively. In addition, coating thickness, surface roughness values, and electrochemical corrosion resistance were evaluated. As a result, coatings were successfully applied under all parameter conditions. Among them, the coatings obtained at 300 V and 60 seconds exhibited the best surface performance, with a thickness of 25.15 µm, a surface roughness of 1.56 µm, a Ca/P ratio of 1.83, and a remarkably low corrosion rate of 0.0000135 mm/year.