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Fabrication of Ni -P -MoS2 Composite Coating by Electroless Deposition and Evaluation of Its Tribological Properties

Majidian, Maryam | 2009

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40540 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Ghorbani, Mohammad; Afshar, Abdollah
  7. Abstract:
  8. Adding solid lubricant particles such as PTFE, Graphite and MoS2, has major influence on electroless composite nickel coatings in order to make low friction surfaces. Among these lubricants, MoS2 has attracted great attention due to its highest stability under wearing condition. In this work Ni-P-MoS2 composite coatings using MoS2 nano-particles have been made and in the next step, we evaluated tribological properties of these coatings. For exploring these coatings different experiments were utilized, like Scanning Electron Microscope study (SEM), chemical composition analysis exploiting AAS and XRF method, and thickness measurements. Two kinds of surfactants, CTAB and PVP, have been applied to the electroless bath in various concentrations to make a suitable suspension needed for set up composite coatings with desired properties. The optimum concentrations were determined for 1 gr/l MoS2, 0.5 g/l CTAB and 3 gr/l PVP. Results show that prepared coatings at these concentrations have maximum amount of particles embedded inside the coatings and homogenous surfaces. By using Pin-on-disc method, wear and friction behavior of coatings were assessed. We observed that adding MoS2 drastically decreases friction coefficient of composite coatings. The minimum coefficient of 0.05 was resulted from composite coatings derived from electroless bath involved 3 g/l MoS2. Annealing of the composite coating at 400 °C for 1 hour had positive effect on stability and wear resistance but increased friction coefficient of the coatings about 4 times. For annealed coatings adding to the amount of loading up to three times more than initial load did not change the friction coefficient and wear resistance of coating considerably. Comparison between composite coatings with nano- and micro- sized particles revealed that nano-composite coatings have more homogeneous morphology, lower porosity, lower friction coefficient and higher wear resistance
  9. Keywords:
  10. Nickel Coating ; Composite ; Electroless ; Molybdenum Sulfur ; Nanoparticles ; Tribological Properties

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