tompoland I started my working life in 1976 working for Scientific Mechanics, they made parts for the defence industry and lasers. They were a super high precision machining company. I first hear about Amorphous carbon coatings then (First invented in 1953), the term DLC (which is misleading) was coined by some researchers in 1971, so this stuff has been around a long time (over 70 years).
You may want to give this a read it’s a little dry, but interesting if you want to learn more about DLC coatings. https://www.researchgate.net/publication/285897475_An_overview_of_DLC_coatings_on_cutting_tools_performance
Care needs to be taken as there are many types, thicknesses and application quality of Amporphous carbon coatings, the advantage is it can make a relatively soft stainless base harder…but like an M&M except the outer shell is literally Microns thick. if that doesn’t adhere properly…well remember that song by Paul Simon, “Call me Al”, they are soft in the middle.
I have seen Chinesium stuff coming off of burrs in the past and the Chinese do not have a reputation for good burr manufacture, quite the reverse. I suspect Italmill may not be supplying them for direct sale grinders from China. If you think hard about it, it’s pretty obvious why they might do this (and have done it before with the Chinese manufacturers of this stable of grinders. Italmill supply a lot of Italian companies, big ones and encouraging competition by supplying the Chinese, might well screw them at home, ultimately their burr market would disappear and they would be out of business. As ultimately the Chinese would copy the burr geometries and manufacture their own…as they are now doing (manufacturing, I don’t know about copying). Plus there are many types of “DLC” coating.
lastly the material burrs are made of is interesting, You see the stainless burrs being massively bigged up, but it’s not an ideal material. It is however, much easier to machine, then it can be nanoscale coated to give it some wear resistance it wouldn’t otherwise have. The quality of this coating is paramount. A tool steel burr is much, much more difficult to make and very hard all the way through. I used tool steel to machine silver steel and stainless steel! Mazzer of course use tool steel burrs, they are v ery hard, flat and extreemly well machined with good burr geometry and I like them a lot they have been making burrs a very long time. There was a short stint decades ago where they used Italmill, but were not happy with the quality and moved production in house.
Lastly geometry is critically important as well as manufacturing quality.. Mazzer burrs have great geometry and are machined to extremely high tolerances (down to a few microns). You can even tell which burr cutting machine a burr was made on!
I’ll finish on this one, as I see a lot of the grinder manufacturers and influencers saying this. “Omni Burrs”, good for espresso or filter..this doesn’t exist. For flat burrs especially, an espresso burr is good for espresso, it’s been made to do that job and requires a certain geometry and characteristics. You can make filter with it, but it’s not great at that job. A filter burr is great for filter, but a properly designed filter burr will be incapable of making espresso…not even so called “allonge” shots should be possible.