Tribo-corrosive wear and mechanical properties of nanoparticles reinforced Mg-AZ91D composites

This study investigates the corrosion behaviour of magnesium (Mg-AZ91D) alloy reinforced with nano metal oxides (ZnO, MnO, and TiO2) using the tribocorrosion methodology. The mechanical characteristics of the materials were investigated using ASTM standards for AZ91D alloy, AZ91D/ZnO, AZ91D/MnO, and AZ91D/TiO2 composites. The AZ91D/TiO2 nanocomposite has higher hardness (122.71 HV) and tensile strength due to decreased porosity and smaller grain size (200.7 MPa). The corrosion behaviour of the fabricated alloys and composites was investigated using tribocorrosion test methods at various NaCl concentrations (2-3.5%). AZ91D/ TiO2 nanocomposite evidenced least OCP drop (-0.7 to-1.0 V) with minimum COF (0.10) at 2.5% NaCl concentration as a result of the development of a thick oxide layer that protected the surface from wear and Cl- environment throughout the tribocorrosion test. Images of tribocorrosion test samples revealed corrosion pit and crack formation. The elemental mapping and EDAX results validate the formation of Mg2TiO3 precipitates on the AZ91D/TiO2 nanocomposite; at the same time, a tribo-corroded surface profile revealed an optimum wear depth of 55 mu m at 2.5% NaCl concentration for the same composition.