friction stir proceesing.........

F

fred w

Joined
Mar 9, 2009
Messages
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anyone know anything about friction stir process.? an article in peterson hunting mag may 2009, pg. 10 talks about a new process for knives, if i understand it correctly some process of high speed rubbing on the cutting edge of the blade 1/2 " up or so toward the spine. produces a rockwell of 65 to 68. they claim d-2 works the best. (their web;diamondbladeknives.com.) doesn't look like its a process for a custom guy, i do think this is proprietary stuff. i also wonder how easy it would be to resharpen.? excaliber finally lives! later fred w
 
Seems rather counter-intuitive when compared to say, the traditional Japanese hardening, where the area near the spine is softer than the edge....what you describe sounds like it would be just the opposite, no? Or does the process result in a uniform hardness throughout the blade?
 
Do a Google search of this site looking for "diamond blade" or "friction forged".
Use the Google "advanced search" option in order to limit your search to a single web site.

There were half a dozen threads about it in ... I want to say summer-fall of 2007. IIRC Cliff Stamp was still here.

The assessment from several members who bought them was that the process produces an exceptional blade. Knives take an incredible edge and hold it extremely well. Very expensive knives, though. Way out of my price range.

Here is probably one of the better threads
http://www.bladeforums.com/forums/showthread.php?t=480424&highlight=diamond

Note: I take pretty much anything Phil Wilson says as gospel.
 
fred w said:
anyone know anything about friction stir process.? an article in peterson hunting mag may 2009, pg. 10 talks about a new process for knives, if i understand it correctly some process of high speed rubbing on the cutting edge of the blade 1/2 " up or so toward the spine. produces a rockwell of 65 to 68. they claim d-2 works the best. (their web;diamondbladeknives.com.) doesn't look like its a process for a custom guy, i do think this is proprietary stuff. i also wonder how easy it would be to resharpen.? excaliber finally lives! later fred w
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Interesting, I was just reading a short blurb in WIRED magazine on Friction Stir Welding this morning. The article was about NASA's friction stir welding rig they are using to join sections of the ARES rocket. The rocket is made of a aluminum alloy which is extremely difficult to weld using traditional methods. A rod is inserted into the seam and rotated to create friction and according to the article causes molecules of the metal to blend together. As an added bonus instead of a traditional weld seam which adds weight, this process actually removes a small amount of material as it works, reducing the overall weight while creating a strong bond (every once counts in spacecraft).
 
no , the article states that the upper part of the blade is less hard ,springy is their term. they claim they bent the blade to a 120 degree angle, from which it came back with no deformation etc. check out the website lots of info. fred w
 
The developers of the process are members here. Maybe they'll chime in. My understanding is that the whole blade is hardened and tempered to a spring temper in the usual manner, then the edge is FSP (friction stir processed), resulting in a very fine grain size with a very hard edge. Reports are that edge toughness is good, the stirred region is stainless, and the edge holding is exceptional, as is the price. I think it would work on any air hardening steel, which D2 is, and would like to see it tried on A2 or even M2. The edge holding comes almost exclusively from the high hardness, as most, if not all, the carbides in D2 are dissolved in the stirred region.
 
My understanding is that it is not so much that the carbides are dissolved, but rather that they are extremely small.

Somewhere in one of the previous threads I asked the Diamond guys if the process changed the grain structure of the metal. They said it did. There is a metallurgist where I work who has done quite a bit of work with friction stir welding. I asked him if friction stirring could do that and he said that it absolutely could. The process makes for an extremely fine grained steel.
 
It would be interesting to know the temperature that the metal actually begins to stir. I assume its considerably higher than the standard hardening temperature for D2. In another thread, I asked the BYU guys about the carbides and at the time they were still quantifying them. I'm sure the carbides are very small, and I suppose that the total volume percent is greatly reduced as well, though I dont know this for sure. My logic is that for the edge to be stainless, which they claim, almost none of the chromium in D2 can be tied up in carbides, thus my guess that the carbide volume percent is greatly reduced, and the remaining carbides are very small, nanometers probably. They (BYU) claim that the grain size is ~500 nm. I guess I'm just going to have to put up and buy one to play with, maybe next year.
 
*snowflake* said:
could you please explain the above statement in more detail?
Click to expand...
Sure:
On my edge retention tests friction forged D2 shows results not better then average. More details on testing:

http://playground.sun.com/~vasya/Manila-Rope-Results.html

My Summit from Diamond blades for $400 was exceptionally sharp, as sharp as I can sharpen myself - it was first production knife which was able to whittle hair. Most people can not do this and so were very impressed. But I can sharpen any knife to same level and when test this one with 27 other knives with same starting sharpness it take 21 place - not better then average.

Thanks, Vassili.
 
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