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Electrodeposition of Ni-P/Cu Multilayer, Mechanism Study, Corrosion and Wear Properties

Hassanpour Youzband, Akram | 2020

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 52764 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Ghorbani, Mohammad; Dolati, Abolghassem
  7. Abstract:
  8. The aim of this project is electrodeposition of Cu/Ni-P multi-layer coating and investigating the nucleation and growth mechanisms of the deposits. To evaluate the effect of the selected bath on the kinetics of the process and deposition, cyclic voltammetry and chronoamperometry studies were conducted and electrodeposition mechanism was obtained three-dimensional instantaneous nucleation and growth controlled by diffusion. Potentiostatic pulse-deposition method with potential steps -0.3 and -1.1 V vs SCE was selected for deposition of Cu/Ni-P multi-layers. In order to demonstrate the effect of monolayer thickness on the properties of the final coating, multiple layers with various monolayers and different depositing times were created. AAS and EDX were used to analyse the chemical composition of the deposits and final coating, XRD for analysing the crystal structures, and FESEM for analysing morphology and cross section of coating. The results of the aforementioned spectroscopy techniques confirmed the presence of Ni-rich and Cu-rich layers with homogenous and spherical nanostructures.In the next stage corrosion and wear properties of the created multi-layer were investigated by polarization method in simulated sea water (3.5%NaCl) and by pin on disk methods, respectively, which were then was compared with the corrosion and wear properties of Cupronickel. Results of wear test showed that showed that the highest specific wear rate (5×10-9 mm2/N.m) was related to Copronikel (70.30) and multi layer coatings had higher wear resistance. As the thickness of the layers decreased, the specific wear rate decreased from 3.5×10-9 to 1.2×10-9 mm2/ Nm, indicating improved wear resistance due to nano-thickness of the monolayers and grain size. The corrosion potential of multilayer coatings with completed monolayers was more positive than copronikel, which increased from -227 to -211 V vs. SCE with decreasing monolayers thickness. In multilayer coatings with uncompleted layers, the corrosion potential is more negative, reaching the value of -298 V vs. SCE, which is smaller than the corrosion potential of Copronikel (70/30), which is 272 V vs. SCE. The corrosion current density of the multilayer coatings is greater than that of Copronikel. Among the multilayer coatings, the multilayer coatings with completed monolayers had a higher corrosion current density and with decreasing thickness of the monolayers the corrosion current density did not change much and was approximately 9×10-7 A/cm2.For multilayer coatings with incomplete layers, the corrosion current density was approximately 3×10-7 A/cm2, which is approximately 30% of the corrosion current density of the other two coatings.Finally, for investigating the heat treatment effect on the phases existing in the multi –layer, annealing was done at 300, 400, and 500˚C. Conducting heat treatment on this multi-layer with the presence of hard phase Ni3P accored simulataniosly with destroying the layered structure which was due to the occurrence of diffusion between the layers
  9. Keywords:
  10. Electrodeposition ; Corrosion ; Wear ; Multi-Layer Coating ; Nickel-Phosphorous Coating ; Cupper/Nickel-Phosphorus Multilayer Coatings ; Nucleation

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