| Chongqing is a typical hilly area with large undulating terrain and steep slopes.Most of the cultivated land has shallow soil and a large amount of shale or mudstone minerals,resulting in high soil viscosity.Due to this special terrain and environmental impact,large and medium-sized agricultural machinery cannot be widely used,and the phenomenon of soil adhesion is not uncommon on the contact parts of agricultural machinery,which has a serious impact on the working efficiency and service life of agricultural machinery.In this context,the research on light simplification and drag reduction and desorption of agricultural machinery has become a major focus.Aluminum alloy is a common alloy material in light and simplified design,and has been gradually applied to some light agricultural equipment such as tiller,rice transplanter,etc.,which greatly reduces the overall quality and energy consumption of agricultural equipment and improves work efficiency.But at the same time,aluminum alloy materials have the disadvantages of insufficient hardness and wear resistance.In the face of complex soil environment,soil adhesion will lead to increased wear of parts,so that aluminum alloy materials cannot maintain a long service life.Therefore,based on aluminum alloys The research on drag reduction and desorption of materials is an important link in the light and simplified design of agricultural machinery.Micro-arc oxidation(MAO)is the most common process in the surface treatment of aluminum alloys,which can greatly improve the hardness and wear resistance of aluminum alloys.Not only that,the unique loose porous structure on the surface of the micro-arc oxidation film and the physical and chemical properties of the oxide in the film provide infinite possibilities for the subsequent modification of the film.On this basis,this paper uses 6061 aluminum alloy micro-arc oxide film as the substrate,and uses various surface treatment technologies and processes to study the drag reduction and desorption modification of aluminum alloy micro-arc oxide film.The specific research contents and conclusions are as follows:(1)Preparation and properties of MAO-LDHs composite membranes.First,the micro-arc oxidation technology was used to treat the aluminum alloy sample with optimized electrical parameters and electrolyte formulation,and a uniform ceramic film was obtained on its surface as the base film.Prepare 80 ml Mg(NO3)2 solution and adjust the p H of the solution to 10 with ammonia water with a concentration of 1%.After crystallization for a period of time,a layer of LDHs crystals is grown in situ on the surface of the aluminum alloy by hydrothermal method.The growth of LDHs on the aluminum alloy micro-arc oxidation film was analyzed by XRD,FT-IR,SEM and EDS.The friction coefficient of the MAO-LDHs composite film was tested by a friction and wear tester,and the friction coefficient of the composite film was analyzed by SEM and EDS.The wear scar morphology and the participation form of LDHs in the wear process were tested.Finally,the bonding degree between the film and the substrate was tested by the film bonding force tester,and the relationship between the hardness of the composite film and the hydrothermal reaction time was tested with a microhardness tester.The experimental results showed that LDHs were successfully synthesized on the MAO film,and the LDHs blocked the micropores on the MAO film,which made the surface of the MAO film smoother and smoother.And in the process of wear,LDHs played an effective wear reduction effect,the friction coefficient curve of the MAO-LDHs composite film was smoother,the whole wear process was more stable,the bonding degree between the composite film and the substrate was good,and the hardness of the film layer increased with crystallization.As the time prolongs,it decreases.As long as the crystallization time is controlled within 24 h,the hardness of the film layer is still about ten times higher than that of the matrix.(2)Hydrophobic modification test and test analysis of MAO-LDHs composite membrane.Hexadecyltrimethoxysilane(HDTMS)was used as the hydrophobic modifier.After adjusting the test method according to the experimental requirements,the MAO-LDHs composite membrane was immersed in the solvent for 15 minutes,and then the samples were placed in a constant temperature drying box to dry for 4hours.After that,the MAO-LDHs superhydrophobic composite membrane can be obtained.The MAO film,MAO-LDHs composite film and MAO-LDHs superhydrophobic composite film were tested and analyzed by contact angle measuring instrument and microscopic 3D topography measurement system.The test results show that the surface of the MAO film is extremely hydrophilic,so the contact angle cannot be measured,and the 3D microscopic features of the MAO film do not meet the hydrophobic conditions;the contact angle of the MAO-LDHs composite film after hydrothermal treatment is 120°,has a certain degree of hydrophobicity,and its 3D morphological characteristics at the microscopic level are also consistent with this result;the MAO-LDHs composite membrane has a contact angle of 154° after hydrophobic modification,and its surface microscopic morphology has been modified and improved.hydrophobic properties.(3)Plug and pull test with soil.The standard purple soil with 25% and 40%moisture content was used for plugging and pulling tests with three samples,respectively.By analyzing the soil adhesion and resistance changes during the process of pulling the samples out of the soil,the hydrophobically modified MAO-LDHs were verified.Drag reduction and desorption properties of composite membranes.The test results show that the MAO-LDHs superhydrophobic composite membrane has the least adhesion to soil,and the average resistance during the insertion and extraction process is the lowest,and with the increase of water content,the drag reduction and desorption effect of the superhydrophobic composite membrane is more obvious. |
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