脉冲电镀制备Ni-cBN复合镀层的性能

Properties of Electrodeposited Ni-cBN Composite Coatings by Pulsed Power Supply

为了探讨工艺参数对脉冲电镀Ni-cBN复合镀层性能的影响规律，以氨基磺酸镍为镀液，调整平均电流密度、脉冲导通与脉冲间歇比在黄铜基材上脉冲电镀纯镍层，找出最佳工艺参数作为Ni-cBN复合电镀的工艺参数，改变cBN粉末添加量制备复合镀层。利用显微维氏硬度计及摩擦试验机测量镀层硬度及磨损量，借助扫描电镜（SEM）及x射线衍射仪（XRD）观察了镀层的分散情况及晶粒尺寸。结果表明：平均电流密度为1～7A／dm2制备的纯镍镀层晶粒尺寸约350—1000nm，其中3A／dm2时晶粒尺寸最小，为412nm，镀层硬度最高，为402HV；镀层择优取向随着电流密度和输入功率类型而变化；脉冲导通与脉冲间歇比为50：200时，择优取向为（200）晶面，残留应力最大，镀层硬度最高，为456HV；当占空比较低时择优取向偏向（220），占空比较高时择优取向偏向（200）；复合镀层中的cBN粉末含量高且分散性好，耐磨性相对较好；未经热处理，镀液中cBN浓度1．0g/L时镀层硬度最高，为506．96HV，镀层中cBN含量为13．3％，耐磨性最好；在经过热处理后，依然是cBN浓度1．0g／L时得到的镀层硬度最高，为531．86HV，耐磨性也最好；另外，热处理显著降低了镀层磨耗损失。

Pure nickel deposition on Cu substrate was carried out in the nickel sufamate bath under different average current densities and Ton/ Toffratios. The optimized parameters were obtained for the preparation of the composite coatings of Ni and nano/microsized cB N particles under different cB N contents in the bath. The hardness and wear resistance of the coatings were measured by micro Vickers hardness tester and abrasion resistance machine,and the dispersion and grain size of coating were observed by X-ray diffraction( XRD)and scanning electron microscope( SEM). Results indicated that the grain size range of the pure nickel layers was 350 ~ 1 000 μm when the average current density was 1 ~ 7 A/dm2,and the smallest grain size of 412 nm and the highest hardness of 402 HV were obtained under the current density of 3 A/dm2. When the Ton/ Toffratio was 50 ∶ 200,the preferred orientation of the nickel coating was influenced by current density and input power type.The preferred orientation face was( 200),and the coating had the largest residual stress and the highest hardness of 456 HV. The preferred orientation face was( 220) when the duty ratio was small. On the contrary,the preferred orientation face was( 200)with the increase of duty ratio. The composite deposition of Ni/cB N had high cB N content and good dispersity and accordingly presented the comparatively good abrasion resistance. Before heat treatment,the maximum hardness was 506. 96 HV when the cB N content was 1. 0 g/L,and the best wear resistance was achieved when the cB N content was 13. 3%. After heat treatment,when the cB N content was 1. 0 g/L the coating had the maximum hardness of531. 86 HV and the best wear resistance. In addition,the heat treatment distinctly reduced the abrasion loss of the coatings.