EFFECT OF STAND-OFF DISTANCE ON STRUCTURE AND MECHANICAL PROPERTIES OF HYDROXYAPATITE COATINGS PLASMA-SPRAYED ONTO CARBON/CARBON COMPOSITES

Plasma-spraying parameters are of crucial importance to the fabrication of high-quality hydroxyapatite (HA) coating for biomedical use. In this paper, hydroxyapaptite was coated onto carbon fiber reinforced carbon composites (C/C composites) by a plasma spraying method. The effect of stand-off distances on the microstructure, phase composition and shear strength of hydroxyapatite coatings was studied. X-ray diffraction (XRD) was used to characterize the phase composition and scanning electron microscopy (SEM) examined the morphology of the sprayed surface and polished cross-sections. The shear strength of the HA coatings–C/C substrates was detected on a RGD-5 electric tension machine. The interface of the HA coating–C/C composites was also detected. Results showed that the extent of melting of particles increased with increasing stand-off distances, while the crystallinity of the HA decreased at a power level of 30 kW. Mechanical bonding plays a dominant role at the interface of the rough substrate and the deformed HA particles.