Abstract
The work aims to improve the corrosion resistance of magnesium alloys. AZ61 magnesium alloy coated with NiCrAl by high-velocity oxy-fuel thermally spraying was used as the intermediate layer and a layer of Fe-based amorphous coating was fabricated on magnesium alloy. The morphology characteristics, microstructure, thermal stability, mechanical properties, corrosion behavior and surface properties of the Fe-based amorphous coating and AZ61 magnesium alloy were investigated by scanning electron microscope, X-ray diffractometer, differential thermal analyzer, microhardness tests, open circuit potential measurement, potentiodynamic polarization tests, X-ray photoelectron spectroscopy and contact angle measurement, respectively. A layer of Fe-based amorphous coating with a thickness of about 200~240 μm was successfully formed on the surface of AZ61 magnesium alloy. The coating exhibited an amorphous structure within the effective resolution of XRD. From the thermal analysis, the crystallization temperature of the coating with extremely high thermal stability was up to 657 ℃. The microhardness of amorphous coating and AZ61 magnesium alloy were 892 HV and 71 HV, respectively, which was increased by more than 10 times of hardness. In simulated seawater, the steady-state open circuit potentials and corrosion current densities of the Fe-based amorphous coatings and AZ61 magnesium alloy were -0.59 V and -1.58 V, 80 μA/cm2 and 4 μA/cm2, respectively. In the simulated acid rain, the open circuit potentials and corrosion current densities of the Fe-based amorphous coatings and AZ61 magnesium alloy were -0.45 V and -1.51 V, 7.27 μA/cm2 and 1.64 μA/cm2, respectively. The surface wetting angle of deionized water in AZ61 magnesium alloy was (59.8±1.5)?, while the contact angle of Fe-based amorphous coating was (74.4±0.6)?. In-situ formed Fe-based amorphous coating on the surface of magnesium alloy can significantly improve the corrosion resistance of magnesium alloy. In addition, the high thermal stability and microhardness imply the improvement of heat resistance and wear performance of magnesium alloy.
Key words
magnesium alloy; high velocity oxygen fuel; Fe-based amorphous coating; hardness; corrosion resistance; sim-ulated seawater; simulated acid rain
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GUO Sheng-feng, LAI Li-min, DING Kai-lu, ZHANG Hong-ju, WANG Jing-feng, PAN Fu-sheng.
Construction and Corrosion Behaviour of Amorphous Coating on Magnesium Alloy[J]. Surface Technology. 2019, 48(3): 40-46
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Funding
Supported by the National Natural Science Foundation of China (51671162), Chongqing Research Program of Basic Research and Frontier Technology (cstc2015jcyjBX0107) and the Fundamental Research Funds for the Central Universities (XDJK2017B054)