Nanocomposite Coatings Pulsed Electrodeposition Preparation Process And Performance Research

Nano-particles possess many special characteristics as light-sized effect, suface effect,quantum size effect and macro quantum tunnel effect.When nano-particles are electrodeposited with matrix metal, they can enhance the microhardness, wear resistance, corrosion resistance and resistance to high temperature oxidation of matrix metal,and can endow metal surface with new performance such as mechanics, calorifics, optics, electromagnetics and so on, so nano-composite coating has sweeping application prospects in the domain of the metallurgy, chemical industry, tobacco and machinery. Compared to direct-current electrodeposition, the pulse current has higher instantaneous current density, therefore, we can prepare multi-dimensional nano-composite coatings showing more excellent physics and chemistry performance by using the coordination superiority of pulse electrodeposition technology and material multi-dimensional composite.In this paper, we had obtained some valuable conclusion, conducting the systematic research on the preparation craft of pulse electrodeposition, microstructure and performance of the Ni-W-P-CeO2-SiO2 nano-composite coatings.While pulse frequency was constant,the influence of pulse parameter on the pulse electrodeposit process of Ni-W-P-CeO2-SiO2 nano-composite coatings was studied, using microhardness, deposition rate and nano-particle content to carry on token. In conclusion, we determined preferable pulse parameter initially, respectively was:positive pulse duty cycle: 10%; positive pulse working hours:300ms; positive pulse average current density:15A/dm2;reverse pulse duty cycle:30%; reverse pulse working time:40ms; reverse pulse average current density: 1.5A/dm2.The change rule of microstructure of Ni-W-P-CeO2-SiO2 nano-composite coatings was studied, indicates:the nano-composite coatings is amorphous as-deposited, but it changes into crystallize and Ni2P, Ni3P phases precipitate when heat treated temperature is 300℃; When temperature is raised to 600℃, Ni3Pand Ni5P2 vanish, the crystal process of coating is finished and the matrix metal is oxidized partially;When the oxidized temperature is lower than 400℃, the Surface microstructure of nano-composite coatings does not have obvious change, but with the increasing of oxidized temperature, the crystal grain of matrix metal starts to grow up,when the temperature arrives at 800℃, the microstructure of coating is still continuous, compact and integrity, and does not strips and falls off.The influence of heat treatment craft on the microhardness of Ni-W-P-CeO2-SiO2 nano-composite coatings was studied, indicates:when heat treatment time is 1h, the microhardness increases with increasing heat treatment temperature, and it reaches peak value at 400℃, but it decreases with increasing heat treatment temperature cotinually;when heat treatment temperature is 300℃, the microhardness increases first and decreases afterwards with the extension of heat treatment time,and it reaches the maximum at 3h; At the identical heat treatment temperature or heat treatment time, the microhardness of nano-composite coatings is obviously higher than corresponding Ni-W-P alloy coating.The high-temperature oxidation behavior of Ni-W-P-CeO2-SiO2 nano-composite coatings was studied, indicates:When oxidized time is 1h, the dynamics curve between oxidized temperature and oxidation film weight of thecoatings conforms to exponential function approximately; when oxidized temperature is 300℃, the dynamics curve between oxidized temperature and oxidation film weight of the coatings conforms to power function approximately; the anti-high-temperature oxidation performance of nano-composite coatings is 2-3 times than of Ni-W-P alloy coating.The corrosion rule and mechanism of Ni-W-P-CeO2-SiO2 nano-composite coatings in the HCl and NaCl corrosive medium was studied, indicates:with the extension of corrosion time, the corrosion dynamics relations between corrosion rate and corrosion time of the coatings is cube function expression; when the density of corrosive medium and corrosion time are the same, the corrosion resistance of the coatings surpasses Ni-W-P alloy coating; The nano-composite coating occurs contact surface corrodes in the HCland NaCl corrosive medium, but Ni-W-P alloy coating occurs slit corrodes in theHCL solution, occurs pitting in NaCl solution.The research content of this paper obtained the subsidization of the national natural sciences fund and Yunnan Province basic research for application plan project.