Titanium carbide differs considerably from other carbides, and is the ideal material for resizing cartridge cases. Titanium carbide has the highest hardness of any readily available carbide. The difference is in the microstructure. Viewed under a microscope it appears smooth and rounded, which presents a slippery non-galling surface, ideal for lubeless resizing of cartridges.
Big Book Catalog, Issue:67, Page:515
Sinclair, Issue:5A, Page:042