Query about finish

B

BB

Would like to hear the pros and cons on bead blast finish vs. "coatings" i.e. black titanium aluminum nitride finishes. I'd like to know a little more than just what these finishes offer for appearance sake?
Thanks,
bill
 
Man, BB, you are probably going to start quite a thread here. My thoughts are I much prefer the coatings over the bead blast. They really seem to do a wonderful job resisting corrosion. On the other hand, I like the appearance of bead blast, (which is it's purpose). People have complained though about the small micro- pitting that the sand blasting leaves behind. They say it has a tendency to attract moisture, and thus, cause corrosion. I have many bead blasted blades, and have never had this problem. But for corrosion resistance, (or stealth), the coatings are great.
 
I asked the question before about the TaAin coating here was the reponses.


MikeTurber
posted 08-18-98 22:19 ET (US)

Well don't try to figure out what WTF means.

OK Microtech and other makers are now making knives with Titanium Aluminum Nitrite coatings. I have a very
good idea of what it is but I have these questions.

Does it ad to the hardness like other coatings?

And why mix Aluminum with Titanium. Sounds kind of funny if you ask me but I am sure there is a good reason.
Can someone explain?

Best Regards,
Mike Turber
Brian lavin
posted 08-18-98 22:49 ET (US)

Mike, I've heard of titanium nitride coating, it bonds to steel at the molecular level and is also used in many
other industrial applications; but I must confess, I've not heard of the one you mentioned and I too woder what
aluminum could add. But I'll bet we've got either an engineer or a chemist out there who'll be glad to explain.
Patrick Seeber
posted 08-18-98 23:34 ET (US)

Okay, I am outta my element, but I will take a STAB at it... {Yuk}

I believe the Titanium Nitride coatings are supposed to be more durable and slippery than the standard
parkerized finishes. I believe that it does bond at the molecular level. The application that I am thinking of is the
use on bolts and firing pins on AR-15's.

If you ask me it sure makes a knife look like the back end of a mule (sorry mule lovers). The gold is really
unattractive... And I have never seen a knife with this coating that didn't look scratched! Duh indeed... Timing is
everything!

Okay, Now where is the expert!
Patrick
Eye
posted 08-18-98 23:41 ET (US)

I had a conversation with someone who knows alittle about this and this is part of what he said....

Please allow me to explain. I worked for the largest coating company in the world for over 6 years involved in the
development of TiAln for cutlery, so these are the FACTS. The coatings mentioned are PVD or physical vapor
deposition coatings. They are applied by placing the conductive substrate into a vacuum chamber and bombaring
the surface with charged particles of the coating material. TiN is Titanium Nitride (gold), TiAlN is Titanium
Aluminum (black to grey), TiCN is Titanium Carbon (various colors including black-Black Ti). The process is quite
complex
and involves ultra high vacuum, high current or laser, and ultra pure gasses. The coatings are deposited very
thin, 1 to 3 microns (1 micron=.000049).The advantages are the extreme surface hardness, and some corrosion
resistance. PVD coatings do not provide supreme corrosion resistance because the coating has grain boundaries
where corrosion sites can start. The greatest advantage of PVD coatings is the edge retention. Cutting edge life
can be extended 10x or more, but it is important that the substrate is of sufficient hardness to support the
coating. TiAln and TiCN are the hardest at an Rc equivalent of mid 90's. Amorphous diamond coatings are the
hardest and have no grain boundaries so they have greater corrosion resistance properties.
However they are VERY expensive so for cutlery it is cost prohibitive at this time. I could go into more detail, but
that's the basic concept.

I talked to him more and got some other info, but that should wet your apetite...

Eye
mjswan
posted 08-19-98 02:33 ET (US)

I wonder if the addition of aluminum is what has changed the physical appearance of Microtech's BlackTi blades.
The coating on recent blades is lighter in color and much rougher than whatever material/process they
previously used. Because of the roughness, my initial thought was that perhaps they were now applying BlackTi
to bead blasted blades rather than satin finished blades.

Anybody know the real scoop?

Regards,
Mike
Larry Chew
posted 08-19-98 08:40 ET (US)

Here are the facts:
Aluminum titanium nitride (AlTiN) was developed for high speed dry machining. The aluminum is stated first
because there is more Al than Ti in the coating. In the machining process the heat generated causes a reaction
with the aluminum causing an aluminum oxide layer to form on top of the PVD coating. This is to increase the
heat resistance and life of the cutter. It is most commonly used on carbide tooling. The color was a secondary
concern. The color can be manipulated by controlling the coating voltage to allow more of the aluminum to be
deposited. The difficulty with this type of coating in a sputtering process is the different molecular weights of
the two materials. Tools with varried geometries will have areas that receive more of one material than the other
and the result is a rainbow or discolored area. The coating is very tough and when you say that it is scratched
what you are usually seeing is another material that abraded onto the surface of the blade. If it is a PVD coated
blade you could try cleaning it with a fine scotchbrite pad. If it is a Black T or other soft coating a scotchbrite
pad will really mess it up, so be sure of what you have.
MikeTurber
posted 08-19-98 12:26 ET (US)

I now feel eduacted. See what a great place this is!

Best Regards,
Mike Turber
Mike Schroeder
posted 08-20-98 12:48 ET (US)

Brian lavin:

quote:

I must confess, I've not heard of the one you mentioned and I too woder what aluminum could add.
But I'll bet we've got either an engineer or a chemist out there who'll be glad to explain.



Well, I'm a Chemical Engineer, and I had no idea what it was before I read the above posts! I guess my one
materials science course didn't cover "Knife Coating Materials 101"

[This message has been edited by Mike Schroeder (edited 08-20-98).]
Brian lavin
posted 08-20-98 22:36 ET (US)

Well, Mike, you're many notches up the scale from me, all my anodizing/ti coating info comes from buying
overpriced aftermarket mtn bike parts !!!!
MikeTurber
posted 08-20-98 23:51 ET (US)

Well the only thing I have learned from this is you can always learn something new. And you guys thought I
knew everything. Or is it I thought I new everything. Oh well either way I learn something new every day. Or
was it yesterday

Best Regards,
Mike Turber
 
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