I would consider graphite moderators under the umbrella of salt facing components.
High Ni alloys such as Hast-N have their own issues - mainly radiation induced Ni -> He embrittlement and tellurium embrittlement. That being said, they are very promising.
One is corrosion/radiation damage to the reactor vessel which is probably made with something like
http://www.haynesintl.com/alloys/alloy-portfolio_/Corrosion-...
The other is that most of these designs have a graphite moderator, and the graphite gets damaged in the reactor environment.