Nanomechanical testing of Alumina-Titanium functionally graded thin coatings for orthopaedic applications

►Nanoindentation at multiple penetration depths allows to the identification of a gradient in mechanical properties in functionally Graded Coatings. ►The ratio between maximum penetration depth and contact depth is assessed to be an alternative wear parameter. ►Three characteristic lengths have been taken into account: tip radius, spatial gradient of coating properties and coating thickness. ►Low load indentation experiments were consistent with results obtained from homogeneous coatings.