TiC Production Research of Sintering TZM Alloy(2)
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- Category: Molybdenum knowledge
- Published on 11 December 2015
- Written by yiping
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From work function change we can know Ti+2CO=TiV+CO2 can happen in standard state, but the reaction work function gradually reduce to around1800K and turn to positive value. However, in TZM alloy carbon will restore metal element to form CO, and there are small oxygen content in the sintering TZM alloy. From the study data we know before sintering TZM alloy’s oxygen content is about 1000uL/L so it will produce litter CO. On the other hand, at 10-2Pa vacuum condition, even produce small amount of CO will be taken away so in this system CO content is very low and reaction rate also very low.
TiH2+C=TiC+H2 can happen at low temperature, but studied TiH2=Ti+H2’s computation structure of table 2 we can learn that at the standard state TiH2 start to resolve at about1000K and at the vacuum condition TiH2 has better stability so the resolve temperature will lower. The experiment shows that at vacuum state TiH2 decomposed will begin at 620K and start to decomposing large amount. Below 700K TiH2 dissociate will decompose to Ti and H2.
Comparing the reaction with Ti+C=TiC found at 1000K△G is -172.97kJ·mol-1 which is smaller than TiH2+C=TiC+H2 reaction’s △G and it is .33kJ·mol-1. At 1000K, if the system produce TiC then the reaction fallow Ti+C=TiC reaction. So even at the low temperature it won’t happen the reaction of TiH2+C=TiC+H2.
In the actually production process, sintering heating and heating preservation is shorter than atomic diffusion. And this reaction is mainly solid-solid reaction of solid diffusion control process at Ti’s melting point 1668℃ and Zr melting point 1852℃. TiC at sintering process formed by Ti+C=TiC this reaction on the grain boundary and other place which is in-situ reaction.
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