Effects of nanosecond laser shock peening on residual stress, corrosion and tribocorrosion behavior of WE43 magnesium alloys

Abstract

Biodegradable magnesium (Mg) alloys are promising candidates for use as next-generation implants due to their similar mechanical properties to natural bones, excellent biocompatibility, and the ability to completely degrade in vivo. However, a great challenge of Mg alloys in physiological environments is their fast corrosion rate and low tribocorrosion resistance, which makes it difficult to ensure adequate structural integrity over the required time for complete tissue and bone healing. In this work, the effects of nanosecond laser shock peening (ns-LSP) processing parameters on the surface tribocorrosion resistance of WE43 Mg alloys was investigated. The laser power densities and overlapping ratios were tuned to control the magnitude and depth of residual stresses and the amount of cold work. The tribocorrosion behaviors of WE43 Mg after the ns-LSP treatment were measured in stagnant blood bank buffered saline (pH of 7.0–7.2) under ∼ 37 °C. The tribocorroded surfaces were characterized via X-ray diffraction, scanning electron microscope and energy dispersive spectroscopy. It was found that the optimum peening effect was achieved at lower laser power density and overlapping ratio, where the corrosion cathodic reaction rate was decreased and tribocorrosion rate was reduced by 47.8%, compared to those of the untreated samples. The established processing-performance (i.e., surface hardness, corrosion and tribocorrosion) relationship in this study could shed light on the future LSP process optimization for enhancing surface properties of Mg alloys.