Investigation of tribological properties of silver nanocomposite coatings

Since friction and wear are omnipresent in every situation of human life ranging from nanoscale to macroscale, their study and finding ways to control them are both challenging and exteremly important. The present work is an attempt to analyze friction and wear between materials with silver nanocomposite coated surfaces. The substrate material was a cobalt-chrome alloy which has possible applications in total joint replacements. Electrophoretic deposition (EPD) is used for deposition of coatings of silver nanocomposites on the base material (cobalt-chrome alloy).; Using a standard reciprocating pin-on-plate tribometer, a series of tests were conducted on coated and uncoated surfaces. The counterface materials used for the tests were Alumina, High Density Polyethylene (HDPE), and Titanium balls. Before conducting the tests, the test surface and the counterface ball are thoroughly cleaned to reduce contaminant effects in the measurement of friction. The experiments were performed under 10 and 20 grams normal loads and selected contact parameters (speed, temperature, relative humidity, etc.) so as to make a comparative study of the results. The friction data from the experiment is recorded using a PC interfaced data acquisition system. Surface characterization is carried out using a Scanning Electron Microscope (SEM), an optical microscope, and a surface profilometer to examine the morphology and thickness of the films and the wear track. The experimental results suggest that thin silver nanocomposite coatings noticeably improve friction of cobalt-chrome/HDPE coated sliding pairs. However, as the coating thickness increases, silver nanocomposite coatings show adverse tribological behavior.