Experimental Investigation Of Nanocomposite Deposits By Electroforming With Rotating Cathode In An Ultrasonic Field

Composite electroforming is a precision manufacturing technology for manufacturing composite materials or parts, which using composite electro-deposition principle and electroforming process. By the replacement of microparticles with nanoparticles in the composite electroforming, the properties of nanocomposite deposits, such as microhardness, anti-friction and wear resistance, high-temperature oxidation resistance, corrosion resistance, can be largely enhanced. However, the nanoparticles were apt to agglomerate during electroforming process, which resulting in the superior properties of the nanoparticles cannot be brought into full play. The ultrasonic-assisted electroforming using rotating cathode could effectively restrain the agglomeration of the nanoparticles, and the comprehensive properties of the composite deposits are expected to be improved.In this dissertation, the experimental research of nanocomposite electroforming with rotating cathode in an ultrasonic field was carried out, using rare earths CeO₂ nanoparticles as suspended particles in electroforming bath. Effects of the electroforming methods and process parameters on the content of nanoparticle in the nanocomposite deposits were investigated. The suitable process parameters of electroforming Ni-CeO₂ nanocomposite deposits are obtained: CeO₂ concentration 40g/L, cathodes current density 4A/dm², athode rotating speed 1200rpm, ultrasonic power 300W, ultrasonic frequency 45kHz, magnetic stirring speed 1000rpm and electroforming bath temperature 45℃. Effects of the electroforming methods and process parameters on the surface morphologies and the crystal orientation of the deposits were analyzed. The composite deposits prepared with rotating cathode in an ultrasonic field exhibit refined crystal grain and compact microstructure. CeO₂ nanoparticles uniformly disperse in the composite deposits. The ultrasonic and rotating cathode could change the preferred orientation of the crystallized grains.The microhardness, friction and wear properties, high-temperature oxidation resistance and corrosion resistance of pure Ni deposits and Ni-CeO₂ nanocomposite deposits prepared by different electroforming methods including nonultrasonic-static cathode, rotating cathode, ultrasonic as well as ultrasonic-rotating cathode were investigated comparatively. The Ni-CeO₂ nanocomposite deposit prepared with rotating cathode in an ultrasonic field exhibits high microhardness, excellent friction and wear properties, high-temperature oxidation resistance and corrosion resistance. It is suggested that the composite deposits have superior properties owing to the cooperative effects of CeO₂ nanoparticles, ultrasonic and rotating cathode.The effect of the nanoparticles, the ultrasonic and rotating cathode on the properties of nanocomposite deposits were investigated. It is shown that the nanoparticle evenly dispersed in composite deposits can improve significantly the capability of nucleation of Ni particles, impede the extreme growth of crystal grains, and achieve purpose of grain refinement. Moreover, the nanoparticle dispersed in the nanocomposite deposits matrix as second phase can also cause the deformation of crystal grain, increase grain sliding resistance, and play the effect of dispersion strengthening. The ultrasonic and rotating cathode could promote the homogeneous dispersion of the nanoparticles in bath, make nanoparticles disperse uniformly in composite deposits, thus refine the grain of deposits and improve the properties of the nanocomposite deposits.In this dissertation, the Ni-CeO₂nanocomposite deposits and the electroforming process of preparing nanocomposite deposits were obtained through experimental research. This research would provide some experimental evidence for the application of ultrasonic and rotating cathode into the nanocomposite electroforming.