The Research On Mechanical Performance And Finite Element Analysis Of Metal-Matrix EP/PU FGM Wear-Resistant Coatings

Functional Gradient Materials (FGM) is a new composite material, which has continuous change in component and structure from surface of the material to depth. The epoxy/ polyurethane (EP/PU) gradient coating/substrate composites have been the focal engineering materials because of high strength, corrosion-resistance and excellent wear resistance of the materials.In this thesis, EP/PU gradient coatings which possesses the properties of both EP and PU is expected by thermal spraying in order to mitigate thermal stresses and to resist wear. The EP/PU transition layer is gradient so that the properties can change accordingly.Based on ANSYS finite element code, the detailed producing process of thermal spraying is simulated by the birth and death of elements for EP/PU gradient coating/substrate composites. The residual stresses are analyzed for the materials prepared by thermal spraying method. Finally, it is simulated that the experiments of nano-indentation and nano-scratch tests for the gradient coating/substrate composites. The results shows:(1) When the gradient composition exponent p=1, the residual stress becomes smaller with the fewer layers. And the thinner the single layer is, the smaller the residual stress is.(2) The detailed producing process of thermal spraying is simulated for the gradient coating/substrate composites. It is found that the temperature goes up suddenly when the materials are sprayed to the top of a subject. Meanwhile the temperature of all layers goes up continuously. The temperature of all layers becomes room temperature at the end of the cooling process. On the other hand, the change of stress field is opposite to that of the temperature field. During the process, the stresses of every layer decrease incessantly. Residual stress at the end of the process is smaller than that during the entire cooling process. (3) With the decreasing of thickness, the coating presents lower friction coefficient and better wear resistance. The results show good agreement with the experimental results in the same conditions.(4) The reduction of interface stress which between the subject and coating is an effective method leading to the improvement of the coating property.