Fretting Wear Behavior of n-Al₂O₃/Ni Composite Coatings Prepared by Electro-brush Plating

n-Al2O3/Ni composite coatings were prepared on 30CrMnSi steel substrate by electro-brush plating,using a nickel brush plating electrolyte containing n-Al2O3 particles (about 30 nm) of 20 g·L-1.Fretting wear behavior of the coatings against GCr15 under the dry sliding condition up to 500 ℃ was investigated on a PLINT test rig.Fretting wear mechanism of the coatings was discussed,based on the morphological observation of the worn surface with scanning electron microscopy.Results show that the fretting regimes of the coating consiste of partial slip,mixed regime and slip.The friction coefficient in the initial stage increase sharply and decrease to some degree in the stable stage.The friction coefficient is obviously reduced with the temperature change from room temperature to 400 ℃,but the friction coefficient increase to some degree when the testing temperature was 500 ℃.Fretting wear resistance of the coatings decrease markedly with the increase of testing temperature,due to the obvious decrease of microhardness of the coatings.The predominant fretting wear mechanisms of the coatings at room temperature and above 200 ℃ respectively are delamination and combination of delamination and adhesion.