Oxidation of borides and carbides with yttrium oxide and tantalum additions

Salvador Manuel Rodriguez Cano, University of Texas at El Paso

Abstract

The study presented here describes an investigation of an oxidation scale of a fully-sintered Y2O3-ZrB2-TiC composite exposed in air at 1173K. Upon oxidation of the boride/carbide, a ZrO 2-TiO2 was expected to form similar to the ZrO2-SiO 2 dual scale of an oxidized ZrB2-SiC. The 47wt% Y2O 3-38wt%ZrB2-16wt%TiC composite formed a dual scale consisting primarily of an Y2O3-ZrO2-TiC inner scale with an outer scale of ZrO2-TiO2-Y2O 3. The samples oxidized with a parabolic layer growth allowing the calculation of the effective diffusion coefficient indicating that the oxidation was controlled by oxygen ingress through primarily the ZrO2-Y 2O3 phase. The oxygen potential between the inner layer and the Y2O3-ZrB2-TiC core was estimated by a thermodynamically calculated phase diagrams of TiC-ZrB2 and Ti-ZrB 2-O2. For comparison purposes, a sample composed of HfB2 - TiC - Y2O3 - Ta sample was also oxidized at a temperature of 1773K. In this case, tantalum does not seem to react with any of the borides/carbides present in the sample. In fact, it is protected by a Y2O3 scale. The rest of the sample oxidizes very similar to the ZrB 2 - TiC - Y2O3 sample; exhibiting the same oxidation mechanism.

Subject Area

Chemical engineering|Mechanical engineering|Materials science

Recommended Citation

Rodriguez Cano, Salvador Manuel, "Oxidation of borides and carbides with yttrium oxide and tantalum additions" (2012). ETD Collection for University of Texas, El Paso. AAI1512596.
https://digitalcommons.utep.edu/dissertations/AAI1512596

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