The preparation of calcium phosphate coatings on a 3D-printed titanium alloy (Ti 6Al-4V) by means of plasma electrolytic oxidation (PEO)

Research provides results on the preparation of calcium phosphate coatings using plasma electrolytic oxidation. Calcium phosphate coatings are applied to titanium substrates measuring 20 x 30 x 2 mm. These substrates are produced using selective laser melting (SLM). Most implants are made of titanium and its alloys because of their excellent biocompatibility. However, they have disadvantages, including limited biological activity, wear, and corrosion resistance. Thus, to investigate the impact of the PEO method and the voltage on the coating characteristics, three different voltages, 200, 250, and 300 V, were used. This study utilized a JSM-6390LV scanning electron microscope (SEM) with an INCA Energy Penta FET X3 system. X-ray diffraction analysis was performed using a PANalytical X'Pert PRO diffractometer. Friction and wear tests were performed with a "ball–disk" setup on a TRB³ tribometer. The surface morphology shows that an increase in applied voltage leads to an increase in the size of the pores. At an applied voltage of 300 V, the PEO coating layer cracked and the surface became uncommonly rough. An elemental analysis of the sample cross-sections reveals the formation of TiO₂ layers enriched with Ca and P at voltages between 200 and 250 V. At 300 V, calcium phosphate layers are observed predominantly on the outer surface. XRD analysis shows the presence of hydroxyapatite and titanium oxide phases. The coefficient of friction and the wear rate largely depend on the morphology, pore size, and density of a layer of the titanium dioxide. Therefore, the sample at 250 V exhibits better wear resistance compared to the other two coated samples. The PEO method shows promise for manufacturing implants with calcium phosphate coatings for traumatology and orthopedics. Titanium implants with these coatings are expected to enhance osseointegration and reduce the risk of implant failure.