Fracture Toughness of Microplasma-Sprayed Hydroxyapatite Coating by Nanoindentation.

We report the fracture toughness ( K) measured by nanoindentation technique at five different loads in the range of 100-1000 mN on the cross section of a highly porous microplasma-sprayed hydroxyapatite (MIPS-HAP) coating. The unique advantage of this technique was that it could evaluate K at a scale comparable with that of the local microstructure of the coating. In spite of high porosity (∼11 vol%), the coating showed a toughness (∼0.6 MPa m) comparable to typical literature data (∼0.5 MPa m) on dense HAP coating. Scanning electron microscopy of nanoindents suggested some plausible reasons for achieving a relatively higher toughness in the coating. [ABSTRACT FROM AUTHOR]