INFLUENCE OF YTTRIUM ON HIGH-TEMPERATURE BEHAVIOR OF FE-CR-AL-Y ALLOYS

We have studied the oxidation behaviour of three industrial Fe-Cr-Al alloys (with or without yttrium) at temperatures ranging between 1200 and 1350-degrees-C. At 1200-degrees-C, the behaviour of these alloys is improved as the yttrium content rises. However, for temperatures higher or equal to 1300-degrees-C, the presence of yttrium seems to be detrimental. In particular, the distribution of this element in YFe9 or Y2Fe17 intermetallic particles allows yttrium to diffuse towards the surface of the product. The high kinetic of this diffusion leads to the formation of oxidized cavities by Kirkendall effect. The results obtained on the 0.14%-yttrium product show that the distribution of this element under the oxidized form could help to avoid this damage.