Effect of Applied Cathodic Potential on Friction and Wear Behavior of CoCrMo Alloy in NaCl Solution

Yong Sun,Richard Bailey

doi:10.3390/lubricants8110101

Abstract

Most of the reported work on the effect of applied potential on tribocorrosion or corrosive wear of metallic alloys in a corrosive environment were conducted at anodic potentials. Limited tests have been conducted at cathodic potentials for comparison purposes or to derive the pure mechanical wear component in tribocorrosion. This work investigated the effect of cathodic potential on the friction and wear behaviour of an important biomedical alloy, CoCrMo, sliding against an Al2O3 slider in 0.9% NaCl solution at 37 °C. High friction was found at cathodic potentials close to the open circuit potential, where mechanical wear played a predominant role in material removal. At potentials more cathodic than the hydrogen charging potential, low friction and low wear were observed. The coefficient of friction (COF) and total material loss decreased with increasing cathodic potential, such that at −1000 mV (saturated calomel electrode, SCE), extremely low COF values, as low as 0.02, and negligible material loss were obtained. Such reductions in friction and wear at increasing cathodic potentials were accompanied with the formation of parallel lines in the sliding track and were gradually diminished with increasing applied contact load. It is believed that hydrogen charging and hydrogen segregated layer formation at the surface are responsible for such a phenomenon. It can also be concluded that it is difficult to derive the pure mechanical wear component in tribocorrosion by simply conducting a test at an arbitrary cathodic potential.

Highlights

Material degradation due to friction and wear in a corrosive environment is a common phenomenon that can be found in many engineering applications, such as in marine, mining, food processing, chemical processing and biomedical machineries and devices [1,2,3]
The effect of applied cathodic potential on the sliding friction and wear behaviour of CoCrMo alloy in NaCl solution has been systematically studied over a wide range of cathodic potentials and applied contact loads
It can be concluded that applied cathodic potential affects the friction and wear behaviour of the alloy in two different ways

Summary

Introduction

Material degradation due to friction and wear in a corrosive environment is a common phenomenon that can be found in many engineering applications, such as in marine, mining, food processing, chemical processing and biomedical machineries and devices [1,2,3]. Studies of such a phenomenon, i.e., corrosive wear or tribocorrosion, have been focused on the interplay between mechanical wear and electrochemical corrosion in a tribo-electrochemical system [4,5,6,7]. Uncertainties still exist regarding the selection of a cathodic potential in the test to derive the pure mechanical wear component during

Methods

Discussion

Conclusion