JOURNAL DE PHYSIQUE IV

Abstract.- The influence of implanted yttrium on the oxidation behaviour of an Fe-20Cr-5Al alloy was studied at 1373 K in air under isothermal and thermal cycling conditions in order to verify previous results obtained at 1473 K which indicated no beneficial effect of this addi-tion. The implanted yttrium substantially improved the scale resistance to spalling, only slightly affected the scale growth rate, and altered the scale morphology. On unimplanted material de-veloped ridged scales, while yttrium promoted the formation ofbuckled oxide layers, the higher the dose the more buckled the scale. After spalling of the scale from yttrium implanted material due to prolonged thermal cycling ridges were growing instead of buckles. These and previous results showed that the efficiency of the implanted yttrium depends on its amount in the sub-strate and on the reaction temperature as well and that there is no simple correlation between the scale thickness and its resistance to spalling. 1. Introduction. The so-called reactive elements (Y, Sc, Ce) in most cases offer an improvement of the oxidation behaviour of the FeCrAl-type alumina forming alloys due to enhancing the scale resistance to spalling [l- 101. The efficiency depends upon the manner of their incorporation into the alloy