Improving oxidation resistance by fabricating micro-rings on the surface: Proof of concept for nickel-based superalloy

The high-temperature oxidation of structural materials degrades their performance and reduces their service life, making oxidation resistance a critical focus. Conventional strategies include introducing protective coatings, which risks delamination, and adding antioxidant elements, which requires extensive trial. In this study, we propose an efficient and effective method to enhance oxidation resistance by introducing non-oxidizing micro-rings on the surface. Due to the volume expansion of oxides compared to the unoxidized metal/alloy, compressive stress naturally develops within the oxide film. The micro-ring on the surface introduces additional lateral constraints to the oxide film during oxidation, effectively limiting the oxide growth within the micro-ring. Herein, silicon dioxide (SiO2) micro-rings were fabricated on the surface of a nickel (Ni)-based superalloy by chemical vapor deposition and inductively coupled plasma etching. The micro-ring has an outer diameter of approximately 60 μm, an inner diameter of 40 μm, and a height of 300 nm. High-temperature scanning probe microscopy revealed that the oxide growth inside the micro-ring was significantly suppressed. After 60 min of oxidation at 700 °C, the average oxide film thickness outside the micro-ring was 300 nm, while the average inside the micro-ring was 230 nm. The oxide growth is reduced by 70 nm, representing a significant decrease of 23 %, and demonstrating the effectiveness of the proposed method in improving oxidation resistance. The surface oxidation, featured by the growth and coalescence of oxide islands, was found to be dominated by the outward diffusion of Ni and cobalt (Co). In the inner oxide layer featured by the absence of γ′ phase, oxidation of aluminum (Al) occurred by inward diffusion of anions. Moreover, γ phase was proven to be a preferential oxygen diffusion path in Ni-based superalloy. •A novel method to tune oxidation resistance by fabricating micro-rings on the surface is proposed.•Oxidation inside the micro-ring was found to be suppressed based on the results of in situ SPM observations.•γ phase was proven to be a preferential oxygen diffusion path in Ni-based superalloy.