| Because of its magic characters different from that of general material, nano-structured material is cared enthusiastically by the world and numbers of relative researches are carried out to impulse the development of many subjects such as material science, electronics, mechanics and physics. Summarizing the development of plasma spray, laser remelting and nano technology, a new nano modification coating technology based on plasma spray, laser remelting is put forward; 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. Analyzing the sintering theory of nano material and the heat conduction theory of laser machining, the mathematic model of grain size growth of nano material in laser sintering is built. The grain sizes of the production under different laser sintering parameters are calculated. Then, according to the calculation, a simplified mathematic model of nano material grain size growth in laser sintering is put forward which could be used in the optimization of sintering parameters, the forecasting of grain size and its control.2. Under the aiding of plasma spraying, series reasonable coating material systems are designed to fabricate alumina, NiCrAl/Al2O3, NiCrAl/Al2O3+13%wt.TiO2, NiCrAl/WC-Co coating. Then, the microstructure, mechanical performance and combination strength of the coating are tested and analyzed.3. A nano-structured coating technology is brought forward. Using nano structured material powder as the coating stuff, laser is employed to remelt the plasma spraying coating basis so that the nano structured powder material could be clad on the surface of the plasma spraying base or infiltrated to the plasma spraying coating. With the technology gotten above, series of nano modifying ceramic coating are fabricated to verify its feasibility.4. The microstructures of the coating series gotten are studied in detail with X ray diffraction, scanning electron microscopy. It is indicated after laser remelting, the density of the nano material infiltrated coating is improved and grain size is decreased greatly. In above researches, it is found that the nano material is distributed among general material grains to form inter-granular structure of the coating. With initial tests, it is shown that nano silicon carbide grains are embedded in the grain of general alumina to form intra-granular structure of the Al2O3+13%wt.TiO2+nano-SiC composite ceramic coating. A pure, thin nano structured alumina layer is manufactured in the surface of Al2O3+13%wtTiO2+nano-Al2O3 composite coating whose combination is nano-nano style. It is also found that the combination between the nano granules in the clearance among grains of the general material is nano-nano style. Thus, it can be concluded that several combination styles exist in the coating structure; its forming mechanism and potential effects on the coating performance are discussed. The distribution and infiltration depth(greater than 70 micron) of the nano material in the coating gotten are tested to prove the technology and the mathematic model built once more.5. 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 spra...
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