Pure carbide is too brittle for a sizing ring or a cutting tool material, so what you actually get is made up of microscopic spherical particles of carbide sintered into a matrix with binding materials that are less brittle. About half a minute into this YouTube video
by a German carbide tool insert maker, you will see piles of powder which are the carbides and various binding and coating materials used in making tool inserts. There is also an electron microscope photo of the carbide spheres.
I expect the reason nickel flaked off cases can "strike" to carbide is the use of nickel in the binding matrix that holds the carbide particles in place. It is a nickel on nickel cold weld that actually allows part of a small nickel flake to stick.
If you live in a desert climate, you know the sand dust can get very fine. That dust can gradually polish the nickel out from between the carbide particles in the matrix, which is the mechanism of the wear. The carbide particles themselves are not worn, but rather are gradually separated from the rest of the matrix.
That said, unless WallyL lives in a desert area and has many tens of thousands of rounds through his die, it doesn't seem likely that wear is his problem. I would suspect his cases have become work hardened to the point of being springy and he just needs new brass or a die that's a little narrower to make them work. A couple of people have experimented with annealing straight wall cases at the mouth area, but it seems like a lot of work when new brass from Starline is affordable and will last through dozens of reloading cycles.