| It was conducted in this paper that the experiments of the brush plating for quick nickeland low stress nickel on the copper matrix as well as the three-layer combination of quicknickel and low stress nickel plating and five-layer combination. The surface and thecross-section morphology of the plated layers were observed and analyzed. The thickness andthe micro hardness of the plated layers were tested and analyzed. Moreover, the heat treatmentand thermal shock test for various plated layer were conducted. The wear resistances, the frictioncoefficients of the plated layer of five-layer combination and the plated layer through a heattreatment and the pure copper were compared.The experimental results show that the thickness of the single-layer quick nickel coatingincreases with the increase of plating time, the macroscopic morphology of the coating varieswith the extension of the plating time. With the plating in15minutes and coating thickness in10μm, the coating deposits faster; when the coating thickness is more than10μm, thedeposition rate slows down; the coating thickness less than12.5μm, the surface of the coatingis bright and smooth, without any peeling, cracking, and other phenomena. Plating increasesto about25min, the coating thickness to about14μm; the part of the sample edge began toappear slightly rough. When the plating time reaches35min, the coating thickness to20μm,loss and separation will appear on the part of the coating surface.After plating the same time, and thickness of the low stress nickel coating is thiner thanthe quick nickel coating, but the law is the same that coating thickness and coatingmacroscopic morphology changes with the plating time. Before25minutes, the macroscopicmorphology of the nickel coating also has obvious characteristics of the mirror, smooth andbright. When the plating time is over25minutes, coarse phenomenon appears.Single-layer nickel plating and the low stress nickel were treated under differenttemperature. The micro hardness was decreased with the temperature increasing of heattreatment. When the temperature reaches200℃, the micro hardness reaches its peak. Whenthe heat treatment temperature is less than200℃, the micro hardness of the quick nickelplating are generally higher than micro hardness of the plating without overheating. Inaddition, the thermal shock test at200℃and500℃were carried out, thermal shock up to45times, the plated layer did not fall off or peel, only the coating surface color deepened with theincrease of thermal shock times.The coating thickness and the micro hardness of the three-layer composite platingspecimen are slight increase with the increase of the total plating time, But the coarse andother undesirable phenomena of the macroscopic surface morphology did not appear. after45times of the thermal shock, the plated layer did not fall off or peel, indicating that the bond between the coating and the coating and between the coating and the substrate is strong.The thickness of the five-layer combination of plating reaches50μm, but the coatingmacro-surface remains uniform, dense, and smooth, as well as likes silver. There aresignificant characteristics of the mirror, no spots, peeling, loss and other adverse phenomena.The cross-section of the layer was lamellar, the micro hardness of the layer reaches438HV.Treated at200℃, the micro hardness of the layer is480HV, the wear resistance increases by78%compared with the matrix, increased by nearly50%compared with the untreated layer.With the same current density, brush speed and brush voltage, the methed of alternativeuse of quick nickel and low-stress nickel plating are adapted to deal with electric plating thicknickel layer on the copper substrate. The thickness every quick nickel coating is not more than10μm, and the thickness of the low-stress nickel coating is not more than5μm, multi-layerplating continues until the thickness of the nickel plating reaches the required. |
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