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 a lloys (with or without yttrium) at temperatures ranging between 1200 a nd 1350-degrees-C. At 1200-degrees-C, the behaviour of these alloys is improved as the yttrium content rises. However, for temperatures high er or equal to 1300-degrees-C, the presence of yttrium seems to be det rimental. In particular, the distribution of this element in YFe9 or Y 2Fe17 intermetallic particles allows yttrium to diffuse towards the su rface of the product. The high kinetic of this diffusion leads to the formation of oxidized cavities by Kirkendall effect. The results obtai ned on the 0.14%-yttrium product show that the distribution of this el ement under the oxidized form could help to avoid this damage.