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- Type of Document: M.Sc. Thesis
- Language: Farsi
- Document No: 40937 (07)
- University: Sharif University of Technology
- Department: Materials Science and Engineering
- Advisor(s): Ghorbani, Mohammad
- Abstract:
- Composite coatings including self-lubricant particles such as graphite, MoS2, Al2O3 and SiC are extensively used to decrease the coefficient of friction of tribo-surfaces. Adding lubricant particles to an appropriate metallic matrix like copper, nickel, lead and their alloys is a suitable option in severe condition –for instance high temperature and low pressure- which liquid lubricants will be failed. Bronze can give various properties such as wear resistance, corrosion and oxidation protection, However cyanide solutions for electroplating process have environmentally limited for plating of Cu-Sn. In this research, a chloride electrolyte for bronze electroplating was developed and effect of some parameters (Cu and Sn ions concentration, pH, current density and complexing agent concentration) on coating composition and process efficiency was investigated. Then, co-deposition of graphite and SiC micron-sized particles during electroplating from the acidic bath was studied. It’s found that for plating the bronze coating including 20wt.% Sn, a bath with 8.9 g/L copper, 17 g/L tin, 38.8 g/L sodium pyrophosphate, pH=3.6 and 10 mA/cm-2 current density has maximum efficiency. Results show that volume percent of particles and tin content in coating increases by rising of particles concentration in the bath. Enhancement of current density also increases the tin content in deposited layer and decreases particles percent in coating. It’s shown that deposition of both particles follows Guglielmi’s isotherm. Meanwhile in presence of graphite and/or SiC particles, corrosion resistance of coatings improves. In addition, corrosion inhibition efficiency of hexamethylenetetramine increases. The presence of 6 %Vol. graphite decreased the friction coefficient of bronze from 0.74 to 0.25, while 4.2 %Vol. SiC decreased it to 0.53. Friction coefficient of the coating with 3.6 %Vol. graphite and 3.4 %Vol. SiC was 0.34, but it had minimum weight loss among these coatings. It’s concluded that graphite reduces hardness of coatings while SiC particles have an opposite effect, exactly. Hardness of bronze-graphite-SiC composite coating is between hardness of bronze-graphite and bronze-SiC coatings
- Keywords:
- Alloy Plating ; Chloride Bath ; Graphite ; Composite Coating ; Tribological Properties ; Bronze Graphite ; Copper-Tin Alloy ; Silicon
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