Effect of nano hydroxyapatite addition on microstructural, mechanical, in vitro corrosion and tribological properties of biodegradable Mg2Zn1Mn/HA composites

Biocompatible magnesium alloys are considered appropriate materials for utilization in orthopedics since they offer a great opportunity to get rid of the disadvantages related to use of traditional metallic implants. Mg2Zn1Mn alloy has recently drawn attention for bioimplant applications due to its favorable corrosion properties. In this paper, the characterization of hydroxyapatite (HA) reinforced Mg2Zn1Mn nanocomposites was done extensively to specify the impact of HA addition on their microstructural, mechanical, corrosion and wear properties. The Mg2Zn1Mn/HA nanocomposites were manufactured with the application of ball milling, cold compaction at 700 MPa and followed by sintering at 560 °C. The microhardness and compression tests of Mg2Zn1Mn/HA nanocomposites were made to clarify their mechanical properties, whereas both electrochemical and immersion corrosion experiments in simulated body fluid (SBF) were performed to identify their corrosion characteristics. Moreover, the tribological properties of these composites in dry and SBF conditions were investigated using the ball-on-disk technique. The compressive yield strength of Mg2Zn1Mn composite with 10 or 15 wt % HA, recorded to be 144 and 145 MPa, respectively, was found to be close to that of natural bone (130-180 MPa). In addition, the incorporation of 15 wt % HA into Mg2Zn1Mn decreased the in vitro corrosion rate by 64 %. The Mg3Zn/15HA composite showed the highest corrosion resistance owing to the occurrence of uniform and more stable Ca–P layer on its corroded surface in SBF. Moreover, increasing the HA content in the nanocomposites substantially slowed down the wear rate in SBF.