Umm, that's doubtful. This isn't oxygen that generates a gas on reaction. You would need to look at the actual conditions at moderate temperature (800-1000F is only ~400-500C) for metal fluorides in contact with diamond films and carbon solubility. Even fluorocarbons tend to actually be moderately stable in these temperature conditions.
Diamondlike film coatings should last longer than carbon or graphite crucibles (since those materials are far softer). Those have been tested, although it would seem that high nickel (rather than floridizing Cr) steel is probably the prefered material. SiC also works and they discuss this, but there are concerns about Tritium absorption for the larger crystal structure and porous sintered components.
Diamondlike film coatings should last longer than carbon or graphite crucibles (since those materials are far softer). Those have been tested, although it would seem that high nickel (rather than floridizing Cr) steel is probably the prefered material. SiC also works and they discuss this, but there are concerns about Tritium absorption for the larger crystal structure and porous sintered components.
For some comments and measurements, see this thesis on metal fluoride corrosion control for reactors: http://fhr.nuc.berkeley.edu/wp-content/uploads/2014/10/06-00...
research on SiC also continues: https://www.osti.gov/servlets/purl/1531263