Effect of Gradient Layer of TiO<sub>2</sub>- HA on Properties of the Ha Coated Ti-6Al-4V

The use of hydroxyapatite (HA) coating on metallic implants has always been a challenge due to a discrepancy between ceramic coating and metallic substrate properties. In this study, functionally graded TiO 2 -HA coating (FGC TiO 2 -HA), with bottom-up composition: 100% TiO 2 , 50% TiO 2 -50% HA, 100% HA, produced by sol-gel method on the Ti-6Al-4V alloy substrate. The XRD, FTIR and DSC results signified desired phase achievement. The quality assessment and scratch resistance of FGC TiO 2 -HA in comparison with control samples (single-layer HA and double-layer TiO 2 -HA coatings) were assessed by SEM and FESEM images and nanoscratch test. According to the tests outcomes, The TiO 2 intermediate layer increases the HA coating’s strength (22%) and surface hardness, while gradient layer of TiO 2 -HA improves (14%) this consequence by progressing the coating integrity.