Influence of coating thickness on wear and corrosion resistance of suspension plasma sprayed zirconium oxide coatings on a ZK60 magnesium alloy

Abstract This study investigated the effect of increasing pass numbers (15, 30, and 45 passes) on the properties of ZrO 2 coatings applied to ZK60 Mg alloy surfaces using the suspension plasma spray (SPS) method. The coatings were extensively characterized to analyze their morphology, structure, and chemical properties. Additionally, potentiodynamic electrochemical corrosion tests and wear performance evaluations were conducted. The findings revealed a direct correlation between the number of passes and wear resistance. The volume loss in the 45 passes coated sample was exceptionally low, showing a 24-fold decrease compared to the uncoated substrate, a 5.5-fold decrease compared to the 15-pass sample, and a 2-fold decrease compared to the 30-pass sample. Furthermore, the hardness of the ceramic layer increased by up to 2.5 times with greater thickness, contributing to its mechanical stability. In terms of corrosion, all coated samples demonstrated significantly superior performance, with the uncoated substrate corroding 7.2 to 9.5 times faster. The coated samples also resisted degradation for over three times longer. Although the corrosion rate did not vary significantly between the different pass numbers, the 45-pass sample exhibited the lowest rate. Overall, the ZrO 2 coating with 45 passes delivered the best combination of wear resistance, corrosion protection, and hardness.