Ni/ZrO_2梯度镀层的制备和性能

Preparation and characterization of Ni/ZrO_2 gradient deposits

采用Watt型镀镍溶液,恒电流电沉积方法制备Ni/ZrO_2梯度镀层。扫描电镜(SEM)测试和X-射线衍射分析表明,沿镀层的生长方向,ZrO_2的含量由0逐渐增加到21％(体积分数,下同),呈梯度分布;Ni和ZrO_2各自在特定的角度分别出现其衍射特征峰,互不干扰,镀层中ZrO_2的含量增高,衍射强度变强。断口分析表明,在梯度镀层的内部,材料的塑性变形能力大,韧性最好;沿镀层生长的方向,断口中的韧窝特征逐渐减小,镀层的韧性下降;在表层的断口中ZrO_2微粒明显增多,呈团聚状态,基本上没有韧窝特征,镀层的韧性最差。Ni/ZrO_2梯度镀层的韧性由外至内逐渐增加,呈梯度分布,其延展性为复合镀层的2.5倍。

By the method of composite electrodeposition, the Ni/ZrO2 gradient deposit with continuous distribution of ZrO2 content from 0 to 21% was prepared at a constant current density. X-ray diffraction (XRD) patterns of the gradient deposit show that the Ni and ZrO2 particle diffraction peaks appear at their own given angles respectively, independent of each other. The intensities of the ZrO2 diffraction peaks increase with the increase of ZrO2 content in the deposit. Furthermore, the toughness of graded Ni/ZrO2 deposit was studied by the impingement test. In the adjacent to the substrate, the material has good plastic deformation, which exhibits a high degree of toughness. With the increase of the deposit thickness, the toughness of the middle zone of the fracture decreases. The outer fracture adjacent to the deposit surface shows that the toughness of the deposit surface is lowest at the surface. Thus, the toughness of graded Ni/ZrO2 increases gradually from the surface to the matrix, and its malleability is 2.5 times as much as that of the composite coating because of the gradient distribution of toughness.