Processing, microstructure and mechanical properties of yttria stabilized zirconia reinforced hydroxyapatite coatings

It has been proved that adding yttria stabilized zirconia (YSZ) to hydroxyapatite (HA) could improve the mechanical properties of hydroxyapatite coatings and reduce the formation of calcium oxide which is brittle and not desirable in HA coatings. In this work, processing, microstructure and mechanical properties of yttria stabilized zirconia reinforced HA coatings have been studied. 30 wt.% yittria stabilized zirconia was added to HA. Two processes were applied. One included ball-milling the mixture of YSZ and HA powders, then plasma spheroidizing ball-milled powders (BMSP) and spraying of the coating. Another included ball-milling YSZ powders, blending with HA as purchased, plasma spheroidizing blended powders (BSP) and spraying of the coating. Experimental results showed that mechanical properties of the BMSP and BSP coatings were improved significantly, comparing to the pure HA coating. HA/YSZ solid solution formed and played a very important role in mechanical properties of yttria stabilized zirconia reinforced HA coatings. HA/YSZ solid solution in BSP coating was more than that in BMSP coating, and the properties of BSP coating were better than that of BMSP coating. Tensile tests showed that unmelted YSZ particles were the potential weakness of the yttria stabilized zirconia reinforced HA coatings.