Effect of internal oxidation pretreatments and Si contamination on oxide-scale growth and spalling |
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Authors: | P Y Hou J Stringer |
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Affiliation: | (1) Materials and Chemical Sciences Division, Lawrence Berkeley Laboratory, 94720 Berekeley, California;(2) Electric Power Research Institute, 94304 Palo Alto, California |
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Abstract: | Internal oxidation pretreatments carried out in quartz capsule with a Rhines pack were found to have a profound effect on the subsequent oxidation behavior of alloys. Specimens of Co-15 wt.% Cr, Co-25 wt.% Cr, Ni-25 wt.% Cr, and Ni-25 wt.% Cr-1 wt.% Al were tested at 1100°C after pre-oxidation treatments. Even without the development of internal oxide particles, pretreated binary CoCr and NiCr alloys oxidized with significantly lower rates. Selective oxidation of chromium was observed on the non-Cr2O3-forming Co-base alloys, whereas on the Cr2O3-forming Ni-base alloys, elimination of base-metal oxide, reduction in the Cr2O3 growth rate, and better scale adhesion were found. These effects were more apparent with pre-oxidation temperatures greater than 1000°C and with longer pretreatment times. Contaimination of Si from the quartz is believed to be the cause. |
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Keywords: | silicon internal oxidation Cr2O3 reactive-element effect |
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