Characterization of Microplasma Sprayed Hydroxyapatite Coating

Microplasma sprayed (MIPS) HAP coatings on SS316L substrates were characterized by x-ray diffraction, Fourier transformed infrared spectroscopy, optical microscopy, scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), atomic force microscopy and image analysis. The coating showed a high degree of crystallinity ~92%, a high porosity level of 20 vol.% and a moderate bonding strength of about 13 MPa. The displacement controlled three-point bend tests and associated results of optical microscopy indicated that crack deflection, crack branching, and also local crack bridging occurred during crack propagation in the coating. The nano-hardness (H) and Young’s modulus (E) of the MIPS-HAP coatings as measured by nanoindentation technique were about 6 and 92 GPa, respectively. The fracture toughness (Kic) of the coating was ~0.6 MPa·m0.5. From the nano-scratch experiments, the critical normal load at which localized microcracking led to delamination was measured to be ~400 mN.