| The content of this dissertation is about the modification of coatings by laser cladding nano-material on plasma-spraying coatings. Introducing Rapid Prototyping into nano material processing, experimental researches on the selective sintering of nano material are carried out systematically, the main work accomplished and conclusions gotten in this dissertation are presented as follows:1 Under the aiding of plasma spraying, reasonable coating material systems are designed to fabricate alumina, NiCrAl / A12O3 , NiCrAl / A12O3 + 13%wt.TiO2, NiCrAl/WC-Co coating. Then , the microstructure of the coating are tested and analyzed.2 Nano ceramic material is infiltrated into plasma-spraying coatings by laser-cladding nano-material. The microstructures of the coating series gotten are studied in detail with X ray diffraction, scanning electron microscopy. It is concluded that after laser cladding the density of the nano material infiltrated coating is improved and superior to density of laser-remelting coating. It is found that the nano material is distributed not only among general material grains to form inter-granular structure of the coating but also in the general material grains to form intra-granular structure.Micro-crack caused by laser will be eliminated greatly.3 Mechanical performances of the ceramic coating manufactured are tested. With the hardness tests, it is indicated the hardness of the nano alumina or nano silicon carbide coating is improved to 1.6-2.5 times as that of the plasma spraying coating. With the wearing tests, it is indicated that low laser power employed, the wearing performance of the coating without nano material increase to 1.3 times as that of the plasma coating, at the same time, the wearing performance of the coating with nano material increase 2.3-6 times as that of the plasma spraying coating, the wearing mechanism is further analyzed. With the erosion tests, it is indicated that the erosion performance of the coating with nano material increase five times as that of the plasma spraying coating. At the same time, the erosion performance is affected by ceramic coating thickness and surface quality.4 Nano-Al2O3 material is pressed to slice and is sintered by laser. With the hardness tests, some process parameters are determinated suitably.Laser-cladding nano-ceramic material creates a new applied future for nano-material. Compared to traditional methods, it has many advantages such as consuming less material, cooling more rapid,laser-cladding many kinds of metal and alloy on other metal and alloy. But it also has some shortages. By more than decade research, laser-cladding technology has acquired immense progress in anti-wear, anti-erotion and anti-oxidation scopes. It also has been put into industrial application gradually. |
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