Properties, Structure And Codeposition Mechanism Of Ni/nano-Powder Composite Coating Prepared By Electro-Brush Plating

Electro-brush plating is an important means in mechanism maintaining and strengthening, and it one of the demonstrate technologies of surface engineering. Electro- brush plating possesses the characteristics of convenient and high efficiency, and it is widely applied in the area of mechanism maintaining and strengthening. However, during the application, it was found that the brush plating coating performed unsatisfied properties in the condition of high temperature and thermal wear. This restricts the application range of brush plating. The study aiming at this problem promotes the present and the development of the composite coating prepared by brush plating. The present of nanomaterial provides the new means to solve this problem. Base on these, a composite coating containing nano- powder is prepared by brush plating in this thesis. The mainly research works lie in the process of nano-powder, the microhardness and the anti-fretting property of the composite coating in different temperature, and the structure of the composite coating. Base on associating the preparing process, the properties, and the structure, the strengthening mechanism and the codeposition mechanism of the composite coating are analyzed. All of these results provide not only the experiment data and the basic theories for the application of the composite coating, but also a new direction of the application of nanomaterial. The major results are summarized as follows: 1. The process of wrapping the nano-particle with metal is carried out for the first time in the area of brush plating to disperse the nano-powder in the composite coating. This method could clearly increase the codeposition volume of nano-powder in the composite coating. The metal layer wrapping the nano-particle is the main reason of the changes that occur in the structure and the mechanisms of codeposition of the composite coating. It also performances the key function in strengthening the properties of the composite coating. This method possesses the characters of agility and widely applicability, and it can promote the present of different composite coatings containing nano-powder. This provides the new practicality means in the area of mechanism maintaining and strengthening. 2. Three kinds of composite coatings consisted by nickel and nano-powders (A1203, SiC, and Diamond) are deposited by electro-brush plating. The nano-particles are wrapped by nickel. The NiINi+nano-powder coatings are harder than the high-speed nickel coating in the temperature region between 23 and 4000C, and under the condition of fretting, the coefficient factors of composite coatings are lower than that of the high-speed nickel coating. The wear depths of the composite coatings decrease obviously in 4OOC. Comparing three composite coatings, the NIINi+A1203 performs the best synthesis properties. In 400C, the microhardness of Ni/Ni+Al203 is 3 times than that of the high-speed nickel coating, and the wear depth is 25% of that of the high-speed nickel coating. 3. Flat morphology and compact structure of the NiINi+nano-powder composite coatings are observed. The cell-like structure is found in the composite coating. The wrapped nano-particles disperse inside the composite coating, and combine with matrix metal very well. It is proved that there are several impurity elements in coating, such as C, N, and 0. 4. It is proved that the composite coatings are strengthened by nano-powder and dislocation, and the strengthen phenomena in high temperature can be explained by the interacti...