The Oxidation Behavior of Ni–15Cr–5Al–xSi (x = 0, 1, 3, 5 wt%) Alloys in Air at 1100 °C
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In order to explore effect of silicon on the oxidation resistance of Ni-based superalloys, the cyclic oxidation behavior of Ni–15Cr–5Al–xSi (x = 0, 1, 3, 5 wt%) at 1100 °C was studied. The results show that the addition of Si promotes the nucleation of metastable and stable alumina, which facilitates selective Al oxidation to enable a rapid formation of continuous metastable and stable alumina scales, which in turn greatly enhances the oxidation resistance of alloys. The addition of alloyed Si can also enhance the adhesion between matrix and oxide scale. It was determined that the optimal Si content for scale adherence was 3 wt%. However, the adhesion between oxide scale and matrix decreased with higher Si content. One reason could be that the volume shrinkage caused by transformation from metastable alumina to stable alumina. The other is an increase in the thermal stresses generated in the scale with higher silicon contents.
KeywordsNi-based superalloy High-temperature cyclic oxidation Silicon content Oxidation mechanism Oxide scale
This research was sponsored by Natural Science Foundation of Guangxi (No. 2015GXNSFAA139252) and National Nature Science Foundation of China (No. 51371059) and Natural Science Foundation of Guangxi (No. 2014GXNSFCA118013).