I have no experience with coated anything other than coated and uncoated carbide. No one coats tool steels for lathes or mills. I love tool steels though, carbide is too hard and difficult to shape; so when doing a project that requires a custom profile for the cutting tool, its always easier to use HS tool steel.
That's also what the bean grinder appears to use... as posted earlier, no one makes burrs out of titanium, its too soft a material and is very 'sticky' so doesn't like to be cut and is difficult to get real sharp. But they do coat carbide bits with Titanium nitride coatings, that's the pretty gold colors. I'm pretty sure the burrs are made from tool steels and then hardened. When my new zip burrs come in, I'll have a set of old burrs I can experiment with, but pretty sure they are D2 or a near equivalent. It would be interesting if someone made a set of burrs from carbide.... they would probably last decades
but carbide is too expensive in those kind of sizes.
I found a very old thread from someone who bought a set of Robur conical burrs and was making his own grinder... from 2011. HB has since revised that thread and put my inquiry on that thread, and I hope the OP chimes in, although its been 7 years since the thread was started. The reason I started this post about the burrs was because I was sort of knocking around some ideas, pricing out burr sets as I was sort of in the planning stages of doing the same thing and building an experimental grinder for myself, thus the questions on burr set costs. Have worked out some of the broad strokes, but now have to find a brushless DC motor with controller. Anyone with a dead power wheelchair they'd like to donate or sell to me parts from, at low cost