Nanoindentation study of microplasma sprayed hydroxyapatite coating

The microplasma sprayed (MPS) hydroxyapatite (HAP) coating on surgical grade SS316L, is an emerging material for bio-ceramic based implant application involving higher reliability. For this purpose, a 200 mu m thick MPS-HAP coating was developed on SS316L substrate and characterized by XRD, SEM and FE-SEM techniques. The local mechanical properties of the coating, e.g. nano-hardness and Young's modulus were evaluated by nanoindentation technique carried out with a Berkovich indenter at various depths in the range of about 170-3000 mn on a polished top surface. The characteristic values of nano-hardness (1.5-5 GPa) and Young's modulus (similar to 60-100 GPa) obtained through the application of Weibull statistics to the experimentally measured data revealed a strong indentation size effect (ISE). Attempts were made to explain the genesis of ISE on the basis of some existing and some new concepts. (C) 2009 Elsevier Ltd and Techna Group S.r.l. All rights reserved.