| Magnesium, aluminum and their alloys have been widely used in the military field due to the merits of qualitative light, high specific strength and stiffness. However, because of their inherent physical chemistry defects, such as high chemical activity, good oxidability, negative standard electrode potential, prone to electrochemical corrosion and low hardness, all kinds of equipments will suffer from different degrees of corrosion after being put into use. The main reason is that, the performance of the surface protective layer currently used is not qualified, so that, there is on forming of effective barrier between the substrate and the external to suppress and alleviate the failure of magnesium alloy. Therefore, it's urgent to explore a new effective surface protection material system and the preparation technology of coating layer.Aluminum based amorphous material, which is well known for scries of advantages, such as low density, high strength, high toughness, superplastic and excellent corrosion resistance, is a kind of new metallic materials with a very broad application prospects. However, the limited glass forming ability and poor plasticity at room temperature limit its application as a structural material. The reparation of amorphous aluminum coating by HVAF is an effective way to solve the above problems.This work based on the excellent performance of Al-based amorphous alloy system, choosing the mechanical properties of the coating and electrochemical corrosion as the research objectives, using scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), X-ray diffraction analyzer (XRD), differential scanning calorimetry (DSC), micro Vickers hardness tester (Vickers Indenter), X-ray three-dimensional imaging system (XRM) and electrochemical workstation (Electrochemical Workstation) and other experimental systems, systematically studied the preparation of Al-based amorphous coating by means of HVAF. Specific content includes the following aspects:1. The A186Ni6Y4.5Co2La1.5 powders prepared by gas atomization,with very little a-Al crystal phase, base to the amorphous structure, smooth surface, good sphericity and low degree of oxidation.2. By using the range analysis to study the samples of amorphous content, porosity, thickness, hardness, bond strength and roughness, the optimum process parameters are as follows:spray distance 24 cm, first scanning speed 3600 mm/s, air pressure 78 PSI, powder coating speed 10 r/s. The coating, prepared by the optimized spraying process, the content of amorphous is 65% and crystallization temperature about 304 ?,which conform to the expected indicators as amorphous content up to 50% and crystallization temperature above 200 ?; The porosity is 2.23%, which is more than expectations as the porosity is less of 1%, and need to be further optimized; The vickers hardness of the surface is 417 HV, which is about more than 3 times of that of the traditional 2XXX series aluminium alloys (about 120?140 HV), and significantly higher than the hardness value of 316L stainless steel used in the industry (about 180 HV); The bond strength is 43.04 MPa, which is far more than 30 MPa as expected.3. The results of electrochemical test results show that:in nitric acid solution, Al-based amorphous coating showed a rapid passivation behavior. Besides, coating porosity, amorphous content and thickness do not necessarily affect the corrosion resistance; In hydrochloric acid solution, the coating thickness has a great influence on the corrosion resistance; In sodium chloride solution, high amorphous content significantly improved the corrosion resistance of the coating. |
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