Microstructure and properties of Ni-Coano-Al_2O_3 composite coatings by pulse reversal current electrodeposition

摘要

Ni-Coano-Al_2O_3 (Ni-Co/Al_2O_3) composite coatings were prepared under pulse reversal current (PRC) and direct current (dc) methods respectively. The microstructure of coatings was characterized by means of XRD, SEM and TEM. Both the Ni-Co alloy and composite coatings exhibit single phase of Ni matrix with face-centered cubic (fcc) crystal structure, and the crystal orientation of the Ni-Co/Al_2O_3 composite coating was transformed from crystal face (200) to (111) compared with alloy coatings. The hardness, anti-wear property and macro-residual stress were also investigated. The results showed that the microstructure and performance of the coatings were greatly affected by Al_2O_3 content and the electrodeposition methods. With the increasing of Al_2O_3 content, the hardness and wear resistance of the composite coatings enhanced. The PRC composite coatings exhibited compact surface, high hardness, better wear resistance and lower macro-residual stress compared with that of the dc composite coatings.