Effect of Current Density on the Microstructure and Properties of Plated Nickel Coating

At the current density of 1-13 A/dm2,Ni coatings were prepared by moving-cathod electroplating technology.The effects of current density on surface morphology,crystallization orientation,porosity,internal stress and microhardness of Ni electroplating were investigated by scanning electron microscopy(SEM),X-ray diffraction analysis(XRD),X-ray stress tester,micro hardness tester,etc.The results show that Ni coatings have different texture and properties at different current densities.When the current density is below 7 A/dm2,the coatings show coarser surface with spherical particles and higher porosity.However,at the current density of 4 A/dm2,Ni electroplating has the lowest tensile stress about 110 MPa.At the current density of 7 A/dm2,the coatings shows uniformity and fine surface spherical particles,and has the lowest surface roughness of Ra 0.69 μm,lowest porosity of 0.08 dot/cm2 and highest microhardness of 330 HV0.1.When the current density is above 7 A/dm2,the surface roughness of Ni coatings increases,and preferred orientation changes from(200) crystal face to(220) crystal face.When the current density attains 13 A/dm2,and the texture coefficient of(220) crystal face reaches 85.4%.