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The Effects Of Uncommon Silicides On The Oxidation Of Alloys From The Nb-Cr-Si System, Daniel Brendan Voglewede
The Effects Of Uncommon Silicides On The Oxidation Of Alloys From The Nb-Cr-Si System, Daniel Brendan Voglewede
Open Access Theses & Dissertations
Niobium based alloys are being tapped as potential successors to current nickel base superalloys in high temperature applications. In the aerospace industry, high temperature materials are constantly being pushed to higher temperature regimes in order to improve engine efficiency however current superalloys cannot be pushed further due to melting temperature limitations. Niobium, being a refractory metal, can withstand much higher temperatures than nickel however its oxidation properties are woefully inadequate.
The purpose of this study is to ascertain whether increased silicon additions can improve niobium oxidation properties by: forming ternary silicides with better oxidation properties and by preventing the formation …
Oxidation Of Borides And Carbides With Y2o3 And Ta Additions, Salvador Manuel Rodriguez
Oxidation Of Borides And Carbides With Y2o3 And Ta Additions, Salvador Manuel Rodriguez
Open Access Theses & Dissertations
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 ZrO2-TiO2 was expected to form similar to the ZrO2-SiO2 dual scale of an oxidized ZrB2-SiC. The 47wt% Y2O3-38wt%ZrB2-16wt%TiC composite formed a dual scale consisting primarily of an Y2O3-ZrO2-TiC inner scale with an outer scale of ZrO2-TiO2-Y2O3.
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-Y2O3 phase. The oxygen potential between the inner layer …