Wear behavior of extruded ZK60 magnesium alloy in simulated body fluid with different pH values

Abstract

Two specimens were prepared along the extrusion (ED) and transverse (TD) directions of the extruded ZK60 magnesium alloy bar, respectively. The wear behavior of ED and TD specimens in air (Dry) and simulated body fluid (SBF) of different pH values (pH 4, 7.4 and 9) was evaluated using ball-on-disk configuration. The wear morphology of specimens was characterized by three-dimensional white light interference profiler, scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The results indicated that pH value had a significant effect on the wear behavior of specimens. The average friction coefficient of ED and TD specimens in each environment decreased in the following order: pH 7.4 ≈ pH 9 > Dry > pH 4, and the wear volume decreased in the following order: Dry > pH 4 > pH 7.4 ≈ pH 9. Abrasive wear and oxidative wear were the main wear mechanisms of ED and TD specimens in air, and corrosive wear was taken place in SBF of pH 4, 7.4 and 9. The formation of Mg(OH)2 film improved the wear resistance of specimen in SBF. The wear behavior of ED and TD specimens in SBF of pH 4 showed an orientation correlation, and the wear volume of TD specimen was greater than that of ED specimen. The effect of pH value and initial texture on the wear behavior of magnesium alloy was discussed.