Experimental Research On Ni-ZrO₂Nanocomposite Coatings By Pulse Electrodeposition With Rotating Cathode In An Ultrasonic Field

Electrodeposited nanocomposite coatings have many excellent properties, such asgood temperature resistance, prominent corrosion resistance, excellent frictionreducing and wear resistant. The concentration polarization could be weakened usingpulse current during nanocomposite electrodeposition. The microstructure and qualityof the coatings can be improved by ultrasound and rotating cathode in nanocompositeelectrodeposition process. It is hopeful to enhance the performance of nanocompositecoatings by using pulse nanocomposite electrodeposition with the organic combinationof ultrasonic field and rotating cathode.In this dissertation, experimental research on nanocomposite coatings prepared bypulse electrodeposition with rotating cathode in an ultrasonic field were carried out, inwhich ZrO₂nanoparticles were used as strengthening phase. The Ni-ZrO₂nanocomposite coatings were prepared successfully and a group optimal processparameter was obtained. The microstructures of nanocomposite coatings wereanalyzed, and the properties of coatings were investigated.Effects of process parameters on ZrO₂content in the nanocomposite coatingswere researched. A group of optimum process parameters for preparation of coatingsusing pulse electrodeposition with rotating cathode in an ultrasonic field was obtainedas follows: ZrO₂concentration （45g/L）, average current density （4A/dm2）, pulsefrequency （666Hz）, duty cycle （0.4）, ultrasonic power （120W）, ultrasonic frequency（28kHz）, athode rotating speed （800r/min）, temperature （45℃） and magnetic stirringspeed （1000r/min）.The microstructures of nanocomposite coatings were discussed. The rules andeffects of various factors on grain refinement, dense structure and preferredorientation were analyzed, in which included ZrO₂nanoparticles, pulse current,ultrasonic field, athode rotating, etc. The microhardness, corrosion resistance, temperature resistance, friction reducing and wear resistant were examined. The rulesand effects of various factors on properties were analyzed.The mechanism of pulse current, ultrasound and rotating cathode acting onnanocomposite electrodeposition was discussed. The concentration polarization ofelectrodeposition was reduced by the pulse current in electrodeposition. Moreover, co-deposited nanoparticles content was promoted. Agglomerates of nanoparticles wererefrained by ultrasonic cavitation and acoustic streaming, and nanoparticles weredistributed uniformly. The cathode hydrogen was cleared by rotating cathode, and thefactors in electrocrystallization were optimized.The results of study will serve as experimental reference for the specific use ofultrasound, rotating cathode and pulse current in nanocomposite electrodeposition.Besides, it could be reference for developing high quality nanocomposite coating.