Influence of current density on nano-Al₂O₃/Ni+Co bionic gradient composite coatings by electrodeposition

Yan Liu1),Luquan Ren1),Sirong Yu2),and Zhuwu Han1) 1) The Key Laboratory of the Ministry of Education of China for Terrain-machine Bionics Engineering,Jilin University,Changchun 130022,China 2) College of Materials Science and Engineering,Jilin University,Changchun 130022,China

摘 要：Metal and nano-ceramic nanocomposite coatings were prepared on the gray cast iron surface by the electrodeposition method. The Ni-Co was used as the metal matrix,and nano-Al2O3 was chosen as the second-phase particulates. To avoid poor inter-face bonding and stress distribution,the gradient structure of biology materials was found as the model and therefore the gradient composite coating was prepared. The morphology of the composite coatings was flatter and the microstructure was denser than that of pure Ni-Co coatings. The composite coatings were prepared by different current densities,and the 2-D and 3-D morphologies of the surface coatings were observed. The result indicated that the 2-D structure became rougher and the 3-D surface density of apices became less when the current density was increased. The content of nanoparticulates reached a maximum value at the current density of 40mA·cm-2,at the same time the properties including microhardness and wear-resistance were analyzed. The microhardness reached a maximum value and the wear volume was also less at the current density of 40mA·cm-2. The reason was that nano-Al2O3 particles caused dispersive strengthening and grain refining.

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