Influence of Preoxidation Treatment on the High-Temperature Oxidation Behavior of an Al-Si Coating on a DZ125 Alloy

The article investigates the effects of preoxidation treatments on the high-temperature oxidation behavior of Al-Si coatings applied to DZ125 alloys, a material commonly used in aerospace hot end components. The study focuses on the microstructural changes and oxidation resistance improvements induced by different preoxidation conditions, specifically Ar-25% H2O and air-25% H2O. Key findings include the formation of dense and smooth alumina scales under low partial pressure of oxygen (pO2) conditions, which significantly enhance oxidation resistance. In contrast, high pO2 conditions lead to the formation of mixed oxide layers, including NiAl2O4 spinel, which are less protective. The distribution of HfO2 particles at the oxide scale/coating interface plays a crucial role in the oxidation behavior, with continuous HfO2 layers improving the undulation of the oxide interface and reducing the oxidation rate. The article also discusses the mechanisms behind these observations, providing a detailed analysis of the diffusion processes and stress relief effects associated with HfO2 formation. The experimental results highlight the importance of preoxidation treatments in enhancing the durability and performance of high-temperature protective coatings, offering valuable insights for the development of advanced oxidation-resistant materials.