Interesting.
Graphitic carbon
sublimes at about 4000K and 101.3 kPa (ie 1 Atmosphere/ 1 Bar)
No liquid phase = no welding together on cooling I presume.
I doubt the carbon brakes actually get that hot - they are more likely to combust to COx in air than they are to change state but for the pedants amongst us, yes yes if the pressure from the brakes gets high enough liquid phase carbon is possible but as that scale runs in units of
kilo atmospheres I doubt that the even best of hydraulics will get us there.
World of Carbon
CW