Friction and Wear Properties of Electrodeposited Ni-La2O3 Nanocomposite Coatings

Ni-La_2O_3 nanocomposite coatings were prepared using composite electrodeposition method. The friction and wear properties of the nanocomposite coatings sliding against AISI1045 steel in a pin-on-disc (?) contact configuration under unlubricated condition were investigated, with the effect of the nano-La_2O_3 content on the friction and wear behaviors of the composite coatings to be emphasized. The worn surfaces of the composite coatings were analyzed using a scanning electron microscope and compared with that of the electrodeposited pure Ni coating. It was found that the incorporation of the nano-La_2O_3 particulates contributed to decrease the friction coefficient to some extent and to reduce the wear mass loss significantly. Moreover, the friction and wear behaviors of the nanocomposite coatings were closely related with the nano-La_2O_3 content. Namely, the nanocomposite coating with a lower nano-La_2O_3 content of 1.1% showed somewhat increased wear-resistance than the pure Ni coating, while the composite coating with a higher nano-La_2O_3 content had much better wear-resistance than the pure Ni coating. The increased wear-resistance of the composite coatings was attributed to the dispersive strengthening effect and grain-size-decreasing effect of the nano-La_2O_3, which made the hardness and compactness of the composite coatings increased, and hence the wear-resistance was greatly increased. Besides, the incorporation of the nano-La_2O_3 particulates also led to difference in the wear mechanisms of the composite coatings as compared with the pure Ni coating. Namely, the pure Ni coating was characterized by severe adhesion wear and scuffing, while the nanocomposite coatings were dominated by slight abrasive wear. This observation agreed well with the corresponding wear-resistance of different coatings. In addition, it was suggested to keep a higher content in the composite coatings so as to acquire the optimal wear-resistance.