Search

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. [ABSTRACT FROM AUTHOR]