What is the chemistry of the Helical Nplus coating?

[dogma]

Does anyone know what the Nplus coating is? https://www.harveyperformance.com/in-the-loupe/category/helical-solutions/

Based on the claimed physical properties and the color I would guess it is some variation on nACRo. Which is a bit of a surprise as I thought that CVD coatings containing Aluminum left the Al chemically reactive so that it could form oxides and thus would be a poor choice for machining Al. What I can say as I've been using the https://www.helicaltool.com/products/tool-type/aluminum-non-ferrous/5-flute roughers and finishers and they are, in my limited experience, the best tools I've ever used. The roughers have the same end grind as the finishers and leave what I would generally consider an acceptable final side finish. The only real downside is you have to be careful with the RDOC because of the shallow gullets... and it seems that Al will weld if you plug them up.

 

[homebrewed]

PVD is a physical transfer of the source material to the substrate (end mills in this case). Via sputtering or, basically, evaporation. CVD is limited to precursors that are gasses, at least at the temperature used in the process, so PVD can deposit a wider range of materials.

The claimed ability to withstand 2012 degrees (centigrade???) might be a push for alumina, which has a melting point of 2072 degrees.

Boron nitride (BN) can go up to 2973C. Boron carbide also is pretty good. There are a number of oxides, like zirconia, which have very high melting points but their physical and chemical properties may not be useful in applications like this. Also, as you mentioned, you want the coating to be resistant to hot aluminum, which probably limits the choices. I'd expect hot aluminum to be a pretty powerful reducing agent so oxides (like zirconia) might not hold up very long. I'm thinking a carbide or nitride coating of some kind. But TiN is a yellow-orange color so that's out.

Sorry, not a definitive answer on my part, just some slightly informed guesses.

 

[dogma]

CVD was a typo on my part. The product page states that its a PVD coating.

The ~1100C tolerance is what really throws me. The claimed hardness (40Gpa!) would make the coating harder than silicone carbide. Why is this only being marketed as a non-ferrous tool coating?

 

[homebrewed]

CVD was a typo on my part. The product page states that its a PVD coating.

The ~1100C tolerance is what really throws me. The claimed hardness (40Gpa!) would make the coating harder than silicone carbide. Why is this only being marketed as a non-ferrous tool coating?

A diamond-like coating (DLC) wouldn't be compatible with steel. At elevated temperatures diamond sort of dissolves into iron (or so I've read). That may be the reason they're restricting its application to non-ferrous materials.

Diamond's hardness is in the range of 40Gpa. That said, DLC usually isn't deposited via PVD. But that might be the only way to do it if your substrate is HSS. The typical deposition method is akin to pyrolysis, closer to CVD in nature -- but the substrate has to be very hot. Again, not compatible with ferrous substrates.

 

[dogma]

The claimed CoF seems way to high to be [only] DLC. I also suspect DLC would be on fire well before 1100C. I wonder if there are some typo(s) in the specs.

 

[pontiac428]

I love it when proprietary technology is so tightly guarded that they won't even tell you the physical principles it employs. It sounds like snake oil- our stuff does this and that, but we won't give you so much as a clue as to how it works. You will never be able to make decisions on the fly without calling the mothership, because you can't predict the coating behavior based on its physical and chemical properties. And good luck troubleshooting without paying them to send a rep to your site. This kind of thing drives me up the wall.