STUDY ON Al-BASED AMORPHOUS AND NANOCRYSTALLINE COMPOSITE COATING

An Al-Ni-Y-Co amorphous and nanocrystalline composite coating was prepared on the surface of the AZ91 Mg alloy by using an automatic high velocity arc spraying system. Its microstructures were analyzed by scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission electron microscope (TEM). The results show that the coatings compose of amorphous, nanocrystalline and microcrystalline phases, which has a compact structure with low porosity about 1.8%. The average Vickers microhardness and bond strength of this coating are 311.7 HV0.1 and 26.8 MPa. Its relative wear resistance is about 10 times than that of Al coating and 6 times than that of AZ91 magnesium alloy. The corrosion potential of this coating is more positive than that of Al coating and AZ91 magnesium alloy, and the corresponding corrosion current density value is about 1/2 the same as that of Al coating and 1/5 as that of AZ91 Mg alloy. Especially, compared with the surface on corroded Al coating and AZ91 Mg alloy, the corroded Al-Ni-Y-Co coating has a more flattered surface with less corrosive piting than Al coating. It is confirmed that the Al-Ni-Y-Co coating is an excellent coatinig with higher wear-resistance and corrosion resistance.