Effect of crystallographic orientation on the tribological behavior of electrodeposited Zn coatings

Abstract

Electrodeposited Zn coatings are used in the automotive and aerospace industries for the cathodic protection of high-strength steel fasteners and components. These coatings are polycrystalline and exhibit preferred orientation depending on the deposition parameters. They undergo varying amounts of contact stress during use and this requires an understanding of the effect of the crystallographic orientation of the coatings on their friction and wear behaviors. In this study, Zn coatings with different orientations were electrodeposited on low-carbon steel substrates by modifying the plating conditions. A reciprocating pin on a disk tribometer with a steel counter sphere under a constant normal load was used to help understand the effect of the orientation of the coating on the coefficient of friction and the sliding behavior of the coatings. Ex situ analysis of the tribo/transfer films was performed using X-ray diffraction, nanoindentation, Raman spectrometry, electron microscopy and nanoindentation techniques. The crystallographic orientation of the coating-tribo/transfer film was correlated with the tribological behavior, strain hardening, and third body formation under contact conditions.