Aluminum Solid-Solution Coating for High-Temperature Corrosion Protection
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Iron aluminide coatings are very resistant to corrosion at 600–700 °C. However, interdiffusion is responsible for a significant reduction of the Al content at the coating surface. A stable diffusion barrier could in principle prevent this degradation mechanism. A new diffusion barrier based on nitrogen was produced and was very effective in reducing coating–substrate interdiffusion on P92. After nitriding P92, an Al slurry was applied and heat-treated, resulting in an overlay coating consisting of an Al solid solution with Cr and Fe. This coating was thinner and quite different from the several Al–Fe intermetallics obtained without nitriding and was fully characterized. A diffusion study was conducted and the results showed that after 2000 h at 650 °C, the new coating suffered very little changes and no interdiffusion with the substrate in contrast with the intermetallic coating deposited without nitriding. Testing under steam and fire-side atmospheres showed promising behavior.
KeywordsAluminum solid solution coating High-temperature corrosion Diffusion barrier Nitriding
The authors are grateful for the support by the Spanish Ministry of Economy and Competitiveness for financial support (ENE2014-52359-C3-1-R) as well as the EC (POEMA, G.A. No.: 310436). The authors also acknowledge all members of the Metallic Materials Area at INTA for technical support, as well as Cristina Gallego and Luis Angurel from the “Consejo Superior de Investigaciones Científicas”(CSIC)—Zaragoza for their excellent microscopy work.
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