DLC Coatings

N

Nebulae

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Aug 24, 2009
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So how are they do they wear well or do they scratch or flake off. Are they better than other coatings like TiN or WC

On a more complex note How are they produced, and why are they so hard.

:) Thanks in advance
 
They don't scratch and they are very hard. However, they don't survive high temperatures. The coating comes off easy at 400 degrees. I believe they use chemical vapor deposition to coat the blade, but it's a trade secret so it's not publicly known.

I find the DLC coating great as an anti-scale compound for hardening steel, though it may also carburize the steel a little bit.
 
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yes I believe you are right about the carburization, this happens during the deposition process as well I think.

from what I have been able to read (which isn't much because must informational materials are scientific papers that you have to buy, or become a member of whatever to view) there are several different methods of coating the blades which I don't understand at all.

As I understand it part the reason they are so hard is that they are essentially diamonds imposed on a substrate or at least the carbon atoms bond in a similar maner as diamond (sp3 hybridization). different elements present in the deposition process increase the adhesiveness of the coating, but can inhibit bonding between carbon atoms resulting in a mixture of Sp2 hybridization and sp3. Sp3 hybrid orbitals have smaller bond lengths and are therefore stronger.

however the matter becomes even more confused with the fact that some of these coatings are not crystalline, but amorphous, Which I also really don't understand

finally the role of other elements especially metals in the coating has me confused as well

http://en.wikipedia.org/wiki/Diamond-like_carbon
http://en.wikipedia.org/wiki/Orbital_hybridisation
 
Yeah there are different structures that sp3 bonds can form. DLC is sp3-bonded but not neccessarily in a cubic lattice. It's not as hard as diamond, more like 80 rc. Synthetic diamond is beyond 100 rc.

They add sp2 carbon to make it less brittle. I don't know what the hydrogen is for, could just be an impurity.

I've never tested it but being sp3 carbon, I think the DLC coating is combustable. I would keep it away from flame and heavy sparks.
 
this is interesting with very little outside information (other than what we or at least I started with) we are able to piece together an intelligent picture of what is going on:)

I think the hydrogen is added to get the DLC to adhere to the surface that needs coating. wich makes sense because if the sp3 bonds are so strong as to make this substance so hard than they would not likely bond with the surface to be coated.

as for the combustibility, i doubt that it would be an issue although you do have a point most sp3 carbon molecules like methane are combustible, but since it is mostly carbon and some impurities i doubt it is particularly flammable
 
So, why would you heat a completed knife blade to 400 degrees?
 
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