In a breakthrough that could redefine the boundaries of magnesium alloy applications, researchers have developed a novel thermal barrier coating (TBC) system that significantly enhances the high-temperature oxidation resistance of these lightweight materials. This advancement, published in the journal *New Particle Journal Materials Degradation* (translated from Chinese), opens new avenues for magnesium alloys in high-temperature environments, particularly in the energy sector.
Magnesium alloys, known for their lightweight and high specific strength, have long been hampered by poor oxidation resistance at elevated temperatures. The native magnesium oxide (MgO) scale formed during oxidation is non-protective, limiting the alloy’s use in high-temperature applications. However, a recent study led by Xuanyi He from the Corrosion and Protection Center at Northeastern University has introduced a game-changing solution.
The research focuses on a novel TBC system, YSZ/PEO/Mg, designed to improve the high-temperature performance of a Mg-Gd-Zn-Zr alloy. This system consists of an atmospheric plasma sprayed (APS) 8YSZ top coat deposited onto a plasma electrolytic oxidation (PEO) bond layer applied to the Mg substrate. For comparison, the team also prepared a YSZ coating deposited directly on the Mg substrate (YSZ/Mg).
During cyclic oxidation tests at 200°C, both TBC systems exhibited stability. However, at 400°C for 100 minutes, the YSZ/Mg coating experienced catastrophic spallation due to interfacial oxidation and thermal stress, exposing the substrate. In stark contrast, the YSZ/PEO/Mg system maintained excellent integrity. “The key to this success lies in the formation of a continuous and protective gadolinium oxide (Gd₂O₃) thermally grown oxide (TGO) layer at the Mg/PEO interface during high-temperature exposure,” explains He. This Gd₂O₃ layer, with a Pilling–Bedworth ratio of 1.29, provides a protective barrier that the native MgO scale cannot.
Moreover, the porous structure of the PEO layer facilitated mechanical interlocking of the YSZ top coat, significantly enhancing interfacial bonding strength. This synergistic effect of the PEO bond coat and the protective Gd₂O₃ TGO layer provides an effective solution for improving the high-temperature oxidation resistance of magnesium alloys.
The implications of this research are profound for the energy sector. Magnesium alloys, with their lightweight and high specific strength, are ideal candidates for applications in aerospace thermal protection systems, automotive engines, and other high-temperature environments. The enhanced oxidation resistance provided by the YSZ/PEO/Mg TBC system could extend the lifespan of components in these demanding applications, reducing maintenance costs and improving overall efficiency.
As Xuanyi He notes, “This approach is particularly promising for applications such as aerospace thermal protection systems, where lightweight materials with high-temperature resistance are in high demand.” The research not only advances our understanding of magnesium alloy behavior at high temperatures but also paves the way for innovative solutions in material science and engineering.
This study, published in *New Particle Journal Materials Degradation*, represents a significant step forward in the quest for high-performance materials that can withstand the rigors of high-temperature environments. As the energy sector continues to evolve, the demand for lightweight, high-strength materials with superior oxidation resistance will only grow. The YSZ/PEO/Mg TBC system offers a compelling solution, setting the stage for future developments in the field.