| Sliding bearing is a key component of the modern machinery. With the rapid progress of modern economy and science technology, we have a sharp increasing demand of bearing material, and the demand of ultra-fine properties of this material. Therefore research on microstructure and properties of sliding bearing material and the further development of bearing materials with excellent properties is the top research focus in recent years. Babbitt metal is a typical bearing material with excellent performance of antifriction, but it is poor in mechanical strength. Thus, it is necessary to improve the bearing capacity of this material. We use compound electro-deposition process fabricated carbon nano-tubes (CNTs)/Sn-Pb composite coating by adding pre-acidized CNTs in the Sn-Pb coatings. This thesis studied the friction and wear properties and the erosion resistance of the fabricated coatings in order to research the antifriction and erosion resistance mechanism. And this may contribute to the further popularization and application of this new coating. The main contents were as follows;(1)Using concentrated sulfuric acid and concentrated nitric acid mixed acid oxidation for the pre-acidization of the raw CNTs to scatter reach a fine dispersion. By changing the proportion of two acid and by SEM morphology analysis of the acidized CNTs, we found that when the proportion of two acid is1:1and the10hours’ultrasonic treatment at room temperature got the best result.(2)Researched the fabricating parameters of the CNTs/Sn-Pb coating, including coating time, current density, adding amount of the CNTs and the stirring speed to the effect of the of composite coating morphologies, hardness and thickness of the coatings. The results shows that, when the electro-deposition time is10-20minutes we have a better quality of the coatings, and when the current density is2A/dm2we got a peak point of hardness of35.3HV10g The hardness of the coating first increases and then decrease with the increasing of CNTs’adding, under a certain current density. And the peak point occurs when the CNTs adding amount is2g/L. While the thickness of the coating decreases with the increase of the CNTs amount.(3)The friction and wear properties of both the CNTs/Sn-Pb composite coatings and the conventional Sn-Pb coatings were investigated. The results indicate that, the friction coefficient of the CNTs/Sn-Pb composite coating is smaller than the Sn-Pb coating under different loads. The friction coefficient first decreases and then increases with the adding amount of the CNTs at a certain load. And the friction coefficient reaches the bottom(0.12) when the CNTs amount is2g/L and it has a best performance of wear resistance. Under different loads, the wear loss of the CNTs/Sn-Pb composite coating is less than it is in the conventional Sn-Pb coatings, and the wear loss first decreases and then increases with the increasing of the CNTs’ amount.(4)This thesis also studied the erosion resistance properties of the composite coatings by the electrochemical experiments and by simulating the working environment of the bearings. The results show that, the CNTs/Sn-Pb composite coating have a higher corrosion potential than the ordinary Sn-Pb coatings in the3.5wt%NaCl solutions, and the passive dissolution current of the composite coatings decreases, therefore the erosion resistance is improved. The SEM morphology of the coatings after been processed at the bearing working environment simulation test shows that the CNTs is not easy reaction with acid and alkali, the CNTs effectively protect the matrix, thus improves the erosion resistance of the composite coatings. |
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