Research On Binary Nanocomposite Coatings Technology By Pulse Electrodeposition In An Ultrasonic Field

Nanocomposite coatings by electrodeposition technology have prominent corrosion resistance, good wear resistance and excellent temperature oxidation resistance. Pulse current being used in nanocomposite electrodeposition not only could reduce the concentration polarization of the cathode surface, but also promote the codeposition of nanoparticles. The aid of ultrasound could effectively restrain the agglomeration of nanoparticles and improve the compactness of nanocomposite coatings. Up to now, most of the nanocomposite coatings have only a single kind of nanoparticles, but few researches on preparation of binary nanocomposite coatings were carried out. Composite coatings with better performance are hopefully to be prepared by pulse electrodeposition in an ultrasonic field, combined with adding two kinds of nanoparticles into the plating solutions.In this dissertation, the experimental investigation on binary nanocomposite coatings prepared by pulse electrodeposition in an ultrasonic field was developed by adding ZrO2and CeO2nanoparitcals into the plating solutions. Effects of the process parameters on ZrO2and CeO2content in the composite coatings were mainly researched. The surface morphology and microstructure were analyzed. The properties were tested. The improvement action and mechanism of process parameters on the microstructure and properties of the composite coatings were investigated. The main works completed and conclusions are presented as follows:Effects of the addition content of nanoparticles, pulse current and ultrasound on ZrO2and CeO2contents in the composite coatings were studied. A group of suitable process parameters for preparation of Ni-ZrO2-CeO2composite coatings by pulse electrodeposition in an ultrasonic field was obtained: ZrO2nanoparticles concentration20g/L, CeO2nanoparticles concentration40g/L, positive pulse average current density4A/dm2, reverse pulse average current density0.2A/dm2, positive pulse duty cycle0.4, reverse pulse duty cycle0.1, positive pulse frequency1000Hz, reverse pulse frequency 200Hz, ultrasonic frequency28kHz, ultrasonic power120W, solution stirring velocity1000rpm, electrodeposition bath temperature45℃.Effects of the process parameters and electrodeposition methods on the crystal orientation of the coatings and the surface morphologis were analyzed. The effect rules of the addition contents of nanoparticles, pulse current and ultrasound on properties were investigated.The microhardness, corrosion resistance, friction and wear properties, high-temperature oxidation resistance of coatings prepared by different electrodeposition methods were examined. The improvement action and mechanism of process parameters on the properties of the composite coatings were discussed, in which included ZrO2and CeO2nanoparticles, pulse current, ultrasound, etc.The mechanism of ZrO2and CeO2nanoparticles, pulse current and ultrasound on the preparation of Ni-ZrO2-CeO2composite coatings were analyzed. Appropriate matching proportion of ZrO2and CeO2nanoparticles could promote the codeposition of nanoparticles with metal ions. Pulse current not only could reduce the concentration polarization of the cathode surface, but also improve the nanoparticle contents in composite coatings.The ultrasound could make ZrO2and CeO2disperse uniformly in nanocomposite coatings, thus improve the compactness and properties of the composite coatings.In this dissertation, the preparation process of Ni-ZrO2-CeO2nanocomposite coatings with excellent properties were acquired through experimental research. This research would provide reference for developing the nanocomposite coatings with excellent properties.