Hi,
I am looking for possible literature discussing the oxidation kinetics of gamma TiAl alloys (with Nb as alloying element) at various temperatures. I am obtaining higher oxidation rates at 800 °C then at 900°C. An explanation of this behavior can be possible by studing the kinetics at various temperature. Arrhenius plots at 800 °C favors formation of Al2O3 layer but unfortunately I am observing a mixed layer of Al2O3 and TiO2. Please let me know if any one has a possible answer or hint for me.
Hi Muhammad,
I myself have long-term oxidation test (2500 h) with gamma TiAl alloy TNM-B1 at 800°C and 900°C carried out. In these tests, the samples were each 24 drawn from the furnace and cooled. I have found that the scale layer stang held at cooling from 800°C and flaked off during cooling from 900°C. The spalling of the scale was the reason of much larger mass loss of the specimen during oxidation at 900°C in comparison with the 800°C samples. In both cases, the color of scale is yellow-brown. This proves that the scale is not just Al2O3 and TiO2 oxides.
Regards
Vadim
Hi Vadim, which kind of furnace did you use? The color-caused "pollution" is coming perhaps from your equipment? You don't need much to generate a color in Al2O3.
I have a similar experience as Dr. Nolze. The GIXRD analysis proved a mixture of Al2O3 and TiO2. No other alloying element oxide can be depicted from the diffraction patterns.
I had a clean electric furnace. The surface of the sample at 900°C test looked like this:
dear Muhammad Naveed
Please go through page 6 of the attached paper to look at the mechanisms of how at high temperature in air, layers of mixed oxides grow by competitive oxidation of the Ti and Al alloying elements, which prevents the formation of a continuous and dense α-alumina layer that would provide an effective oxidation barrier. On the contrary, γ-TiAl alloys form a continuous alumina scale in pure oxygen up to 1000°C. it is very helpful.
Thanks for you
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