ISSN:
1573-4889
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract The oxidation behavior of Ni-13.5-33.7Cr-1ThO2 alloys in flowing oxygen at 150 Torr was investigated in the temperature range 1000–1200°C. Gravimetric measurements of the oxidation kinetics have been combined with microstructural studies of the reacted samples in order to evaluate the reaction mechanisms. The oxide products formed on the alloys were a function of Cr content, sample surface preparation, reaction time, and temperature. The presence of ThO2 appears to produce two effects during alloy oxidation. First, enhanced Cr diffusion to the alloy surface results in rapid formation of a Cr2O3 subscale beneath NiO on Ni-13.5Cr-1ThO2 and selective oxidation of Cr for Ni-22.6Cr-1ThO2. Second, the mechanism of formation of Cr2O3 is apparently different from that for simple Ni-Cr alloys, resulting in about an order of magnitude reduction in the Cr2O3 growth rate. The oxidationvaporization of Cr2O3 to CrO3 becomes rate controlling for the higher Cr alloys after only a few hours of exposure at 1200°C.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00604044
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