(above) Grumpus, thanks, good info! Tungsten carbide, wow, it wouldn't surprise me at all if someday some rims had embedded diamond dust, as this has become common for some knife sharpening plates, even with mined diamonds, and now, synthetic diamonds have been on the market for years. When I was back in industry, research was looking at diamond coatings in place of chrome plate for high wear applications. I know some zirconia-based coatings are on the market for protecting, of all things, concrete.
I'd love an easy way to restore the hard anodizing on rims (and aluminum cookware). My cheap rims, I think didn't even come with that.