I don't recall that there is any documented cases of melted VA inside a turbine blade
I'm glad you said that....
I've seen various 'melting points' for VA mentioned, some early in this thread. However, since they were considerably
lower than the figure I 've now been told for the max air temperature in the cooling ducts, I sort-of discounted most of these lower numbers as incorrect - otherwise, as you suggest, VA
would have melted and evidence would surely have been produced from previous encounters. The other problem is that glassy materials with high silica content don't have a 'melting point' as such - they soften / liquefy over a range of temperatures.
But saying that such-&-such could not have happened is not the same as failing to find evidence that it ever did.....
I'm not in a position to clarify this and further speculation would not add value. But I, for one, would like to hear more from people who do know the correct answers. An information vacuum seems to have occurred!