Effects of Additions of Rare Earths and Some Reactive Elements on the High-Temperature Oxidation Resistance of Fe-20Cr Alloys

Effect of La, Y and Al Additions on the High-Temperature Oxidation of Ni–20Cr Alloy

“…However, La and Y additions lost their improving effect in both alloys at 1373 and 1473K, where the best improvement was obtained in the alloys with Al and Si forming a dense internal oxide layer at the scale-alloy interface. From these results and our model proposed previously (2), it was anticipated that a simultaneous addition of rare earths having a strong affinity for oxygen and reactive elements, such as Al and Si, having a high diffusivity in the base alloy would significantly improve the oxidation resistance of both alloys. This anticipation was confirmed on Fe-20Cr alloys with the simultaneous additions of rare earths and reactive elements, La-Al(5), La-Si(6) and YSi(6).…”

The Effects of Rare Earths and Reactive Elements on the Oxidation Resistance of Ni–20Cr Alloy

“…Internal oxidation experiments using an encapsulation method, where Ni-20Cr-0.7M alloys were sealed with Cr-Cr2O3 mixed powder compact in a quartz and held isothermally to allow internal oxidation to occur, also revealed that the growth rates of internal oxide layer depth in Ni-20Cr-0.7M alloys were incomparably slower than those measured previously in Fe-20Cr-0.7M alloys (16). Since the difference in N(O)M between Ni-20Cr-0.7M and Fe-20Cr-0.7M alloys is not large enough to account for the incomparably large difference in the growth rates of internal oxide layer depth, the difference is considered mainly due to the difference between the diffusivities of alloying elements or oxygen in these two alloys.…”

“…Although the amounts of additional elements have been fixed in 0.7 mass% both in the present and previous studies (16), in order to make clear the improving effect of the alloying elements on the oxidation resistance, it seems reasonable to compare the effects of alloying elements by fixing their contents in at%.…”