Engineering the tribological performance of WE43 magnesium alloy through reactive sputtered Nb₂O₅ coatings

Magnesium alloys, such as WE43, have attracted considerable attention for temporary biomedical implant applications owing to their biodegradability, favourable mechanical properties, and inherent biocompatibility. Nevertheless, their practical implementation remains constrained by corrosion and mechanical wear accelerating material degradation. In this context, surface modification strategies have emerged as a promising approach to enhance the stability of WE43 while preserving its biodegradable characteristics. This study investigated the influence of environmental conditions on the wear behaviour of uncoated and Nb₂O₅-coated WE43 alloy under dry sliding in air, both without and following 1 h of pre-immersion in 0.01 mol L^-1 NaCl solution. The results demonstrated that the Nb₂O₅ coating can improve the wear resistance of the WE43 alloy under both tested conditions, reducing wear depth by approximately 47% and wear volume by nearly 35% during tests performed in air. For the dry wear tests after 0.01 mol L^-1 NaCl solution exposure, the coated samples exhibited an even more pronounced improvement in wear volume (nearly 36% reduction) and wear track width (approximately 44% reduction) compared with the uncoated alloy, although the reduction in wear depth was more modest (∼8%). Concomitantly, the coefficient of friction remained relatively stable for all conditions, indicating that the improved tribological performance was mainly associated with the protective character and load redistribution capacity of the Nb₂O₅ layer rather than with friction reduction. These findings demonstrate that Nb₂O₅ coatings can improve the tribological durability of WE43 and potentially enhance its lifespan as a temporary implantable device.