Diamond will help you refine the carbides themselves, but are also pretty aggressive and can make it easier to leave a pretty persistent burr. if you stop at around 2000 grit, you’re not so much refining the carbides as allowing a carbide rich edge to remain and believe me it’s still definitely sharp enough for kitchen work, especially for produce. if you can’t find a diamond stone and want one, the perforated DMT diamond plates are quite good in my experience. I use them extensively for woodworking, chisels and plane irons. fine and extra fine grits are pretty good for kitchen knives. Stay away from the extra extra fine. They used to be good, but the current production seems to be lacking in consistency. I actually have an open ticket with DMT complaining about one of these. The solid DMT plates are kind of dog **** and I don’t like them. Not flat, inconsistent grit.
aluminum oxide. It’s probably the most common abrasive in sandpaper and synthetic sharpening stones. From what I understand it is also an abrasive component in some Japanese natural stones. The stones that are more highly prized have a little bit higher concentration of aluminum oxide compared to silicon dioxidefrom what I understand it is also an abrasive component in some Japanese natural stones. The stones that are more highly prized have a little bit higher concentration of aluminum oxide compared to silica grit. this makes them a bit harder, and able to cut harder material for longer.
Silicon carbide is another common material, and it’s found in things like Norton crystolon stones.
You can also go up the food chain in hardness a bit to ceramics. 3M cubitron paper uses ceramic abrasive. A lot of 2 x 72 grinding belts do the same. Especially the coarser ones.
silicon carbide is more brittle than aluminum oxide, and I think at least from my experience aluminum oxide and ceramic can leave slightly sharper grit particles than silicon carbide, which can leave a more aggressive feeling edge, and cut faster. I feel like silicon carbide can round over a bit. But that is total speculation on my part.
If you stop at the 2K, you’ll be good to go. I honestly have the trouble getting the synthetic natural to perform super well. Somedays I feel like I’ve got the knack, and some days I feel like an idiot. The 2K never lets me down. Another trick I like to do is go to the BBW after the 2K. that helps me deburr cleanly, then I go back to the 2K for one or two light edge leading swipes to bring some of the aggression back.