Effect of nitrogen on the formation and oxidation behavior of iron aluminide coatings

The present study focused on the effect of N in ferritic Fe–9Cr–1Mo and austenitic 304 L alloy substrates on the formation and cyclic oxidation behavior of aluminide coatings fabricated by chemical vapor deposition (CVD). Relatively high N contents in the commercial alloys caused the formation of AlN precipitates in the CVD aluminide coating, which adversely affected the adhesion of the as-deposited coatings, particularly on 304 L. The reduction of N content in the substrate alloys resulted in a cleaner coating layer with fewer precipitates and Kirkendall voids. However, the cyclic oxidation behavior of the aluminide coatings in air + 10 vol.% H2O at 700 °C was not noticeably changed by the N reduction.