TiO2 Sol strengthened Cu-Sn-PTFE composite coatings with high homogeneity and superior resistance to wear

Abstract

Electrodeposited composite coatings consisting of reinforcement, solid lubricant and tough metallic matrix usually exhibit excellent tribological properties, including high resistance to wear and corrosion, low coefficient of friction, and other desired properties. However, if the distribution of the reinforcement is not homogeneous due to particle agglomeration, especially for fine or nano-sized particles, the performance of the coatings could be largely deteriorated. In the work, Cu-Sn-PTFE-TiO2 composite coatings were made using a pulse electroplating process. Homogeneous distribution of TiO2 particles in the coatings was achieved using highly homogeneous dispersion of nano TiO2 Sol in the plating solution rather than directly dispersing the TiO2 nanoparticles in the solution. Such fabricated Cu-Sn-PTFE-TiO2 coatings showed smooth surface, refined grains and high micro-hardness, leading to excellent tribological properties and corrosion resistance. However, too much TiO2 Sol led to changes in the solution’s pH value, accompanied with agglomeration of the TiO2 Sol, lowering the quality of the coatings with decreased resistance to failure during sliding wear tests. This study demonstrates that application of nanoparticle sol in a proper concentration range is an effective new approach to achieve homogeneous distribution of reinforcing nanoparticles in electrodeposited composite coatings for high wear resistance, low friction and corrosion resistance.