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Investigation of Si3n4 Nano Particle Addition on the Hardening Behavior of Anodized Coated 1050 Aluminum Alloy

Mohammadi Dehcheshmeh, Iman | 2014

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 47129 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Afshar, Abdollah
  7. Abstract:
  8. In the present study, it has been tried out to increase the hardness and wear resistance of anodized aluminum coating byadding Si3N4 nanoparticles to the anodizing bath and making a composite coating. In order to investigate the influence of other effective parameters on the properties of anodized coating before the compositing process, hardness and thickness were optimized in the Sulphoric/oxalic bath using design of experimental method (central composite design). The properties of these coatings are dependent on various parameters among which time, temperature and pulse current parameters (current density limit, frequency and duty cycle) were considered in the present study. Analysis of variance (ANOVA) was used in order to optimize the results of the design experiment for predicting the properties of aluminum anodize coatings. Experimental results showed that the temperature and interaction of quadratic behavior of minimum current density with frequency and duty cycle were the most important terms influencing the hardness of anodized coating. Furthermore, it was found that the maximum hardness of this coating was 564 Hv, which was attained at the maximum and minimum current densities of 4.79, 1.14 A/dm2, a frequency of 76.43 Hz, time of 34.48 min, duty cycle of 60.47% and the bath temperature of 1.7 oC. In addition, results showed that temperature and duty cycle are the most important terms affecting the thickness of these coatings and in the maximum current density of 6.09, minimum current density of 1.65, duty cycle of 81.46, a frequency of 327.27, time of 51 min, temperature bath of -2.6 oC, a layer with the thickness of 75.09 µm was produced. The addition of 5 gr/lit Si3N4 nanoparticles to the anodizing bath increased the hardness from 564 to 704Hv.X-ray diffraction analysis and scanning electron microscopy observations confirmed the presence of these particles in the coating. Corrosion behavior of these coatings showed better properties of the composite coatings than the anodized one because of the presence of Si3N4 nanoparticles in the coating. Pin on disk method was used in order to study the wear resistance of the coatings. The result showed that the presence of an anodized coating can be resulted in 72.78%, decreasing of the weight loss compared with the bare aluminium. However, compared with the anodized coating, making a composite coating by the application of Si3N4 nanoparticle was associated with 47.48% decreasing of the weight loss. This observation was attributed to the differences between the friction coefficients which were0. 85, 0.55 and 0.25 for the bare aluminum, anodized coating and composite coating, respectively
  9. Keywords:
  10. Hardness ; Silicon Nitride ; Experiments Design ; Corrosion Resistance ; Anodizing ; Experimental Design ; Wear Resistance ; Composite Coating

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