"Friction Forged" blades--anybody tested one?

Larrin said:
Goddard uses a scale and a pre-determined number of pounds of pressure for when he stops, how precise a stopping point do you want?
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Much more sensitive than that for reasons I noted in the reviews. You also need multiple runs on different cord + sharpenings to produce a stable average. Again, blunting is highly nonlinear and thus you can get massive differences in cut lengths with small changes in sharpness. Check the numbers in the reviews for details.

-Cliff
 
Will, Thanks for bringing this to our attention. The friction weld process has been around for a while. It is has application welding studs to steel plate for imbed in concrete for example. The advantage is that the weld metal is not exposed to air and impurities and therefore makes a cleaner stronger weld. How this applies to "forging" a knife blade will be interesting to learn about. The variables in play for making a blade cut longer are geometry, sharpening, hardness/toughness as you know. If this process improves the grain structure then one could see how the hardness could be increased with still reasonable toughness allowing a thinner sharper blade in the first place. I don't know any of the details on this new process and it may not be fair to question it at this point but I guess I would wonder why not use a finer grained steel in the first place rather than go though a complicated process to improve D2. The new CPM D2 is finer grained allowing a higher working hardness for example. We will have to wait and see how it works out in actual practice in the field. Keeping an open mind, PHIL
 
Broos said:
The science is real, because these two Mech Engineering professors have published a number of papers and have at least one patent for a new method for Friction Stir Welding (FSW), a relatively new welding technique that uses a spinning tool to create a weld with superior properties (compared to fusion welding). It is a solid state process (it plasticizes and joins the material being welded without melting it) that in the past was only used for low temp metals (like Al), and these guys are at the forefront of FSW with high temp metals (steel).

That said, I'm still wondering specifically how it would make a superior knife. The advantage to FSW is that it doesn't create a weak area at the weld with cast or embrittled material like fusion welding does. While I don't understand the advantages as far as making a knife, I suspect they are making a knife with an edge that has been through this process (just speculation).

I'll be looking forward to finding out more.
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The Eclipse 500 is a new airplane that uses friction stir welding extensively to fabricate the fuselage. Pretty cool - the process looks like a giant 3-D milling machine, but the spinning tool simply applies pressure and friction. The metals almost "magicly" join together.

I don't see what this has to do with forging. Guess we'll all have to wait for the product release!
 
tnelson said:
It is interesting how people immediately start poking holes in things before the real technical stuff is released. I know there have been a lot of mishaps in the past where improved performance has been claimed but little delivered. Some of these previous mishaps were published/released prematurely, e.g. without careful testing and analysis. However, it appears that the FF technology has much more peer review from the science community (thanks Broos and HardHeart for finding, and sending, the information along).
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Hi TNelson!

Extraordinary claims are being made and evidence to support those claims isn't being given. That's precisely the type of stuff that attracts skeptical comments like so many flies. That it's peer-reviewed doesn't mean much, either. How many peers were friction forging D2 hunting knives? It's just an appeal-to-authority statement used in place of a valid argument and should be ignored as such.

Could it be the coolest, neatest process and blade steel out there? Maybe. Hopefully it is. Can't tell from the ad, though.
 
Phil,

The stud welding process you are talking about is quite a bit different than the friction stir welding process (FSW). Looking at the literature, FSW uses a rotating tool to generate very localize heat, via friction. Then very high loads are applied along the tool to generate the forging pressure. (www.twi.org.uk)

Friction stir processing (FSP) or friction forging (FF) appears to be the same as the FSW process, except nothing is being welded together. From the literature, FSW and FSP produce some dramatic changes in the microstructure immediately beneath the tool.

Thom,

I agree: evidence isn’t out yet. Based on who was at the kick-off meeting last week, it think we’ll get a good review soon. It will be interesting to see what some of the experts say.

Here are a rew of the tidbits shown at the “Friction Forged” blade kick-off meeting last week: 1) grain size less than 500 nanometers, 2) hardness between 66-68Rc, and 3) a FF D2 blade put in a vise and bent to >110 degrees without chipping, cracking or breaking (A comparable D2 blade at Rc 59-60 only achieved about 60 degrees before breaking).

TN
 
Wow, those are big claims, I never would have guessed that, and I'll be interested to hear confirmation of those numbers, TN. If that is true there will be some buzz. Hard to believe it's that hard and that flexible. If it's true I hope they make the steel available to knifemakers.
 
TNelson,

The grain size combined with the hardness sounds very exciting. The bending, well, did I mention that the grain size and hardness sound very exciting?
 
Tn, thanks for the info. As I said I will keep an open mind. One thing that jumps out at me though is 68 RC on D2. Not sure there is enough carbon in there to suport that hardness especially if any tempering at all is done. If it is 68 then it will cut like crazy I am sure. PHIL
 
Broos said:
Wow, those are big claims, I never would have guessed that, and I'll be interested to hear confirmation of those numbers, TN. If that is true there will be some buzz. Hard to believe it's that hard and that flexible. If it's true I hope they make the steel available to knifemakers.
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From what I heard here, it is not the steel but the process. It almost sounds like (implication or assumption on my part anyway) it will be available in more than one type of steel, but D2 is the one they tested.

Rc of 68 for D2. Is that even possible? Is the Rc constant through out the blade includng within the center of the steel(no case hardening)?
 
tnelson said:
Here are a rew of the tidbits shown at the “Friction Forged” blade kick-off meeting last week: 1) grain size less than 500 nanometers, 2) hardness between 66-68Rc, and 3) a FF D2 blade put in a vise and bent to >110 degrees without chipping, cracking or breaking (A comparable D2 blade at Rc 59-60 only achieved about 60 degrees before breaking).
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That grain size is far less than carbide size in conventional D2. What is the average carbide size in the FF D2?

Cobalt said:
Rc of 68 for D2. Is that even possible?
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Yes, you would just have to dissolve enough of the primary carbide to free up the carbon, then use a very fast quench plus cold to minimize the retained austenite.

-Cliff
 
Cliff Stamp said:
That grain size is far less than carbide size in conventional D2. What is the average carbide size in the FF D2?



Yes, you would just have to dissolve enough of the primary carbide to free up the carbon, then use a very fast quench plus cold to minimize the retained austenite.

-Cliff
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And then give up on the tempering process as well. At which point you will have no stress relief whatsoever. Also, a high chrome high carbon steel like D2 at such a high hardness would be as hard to sharpen as 440V and if you have ever had 440V you know what that means. Not even cru-wear or vasco-wear compare to 440V for sharpening problems. But it does outlast everything else I have ever used.
 
No you would still temper, 325-375C or so. Yes the grindability would be low, more so due to the carbide than the hardness. But this should not be a factor in use of the knife given proper suitability to the tasks of the blade and geometry. Since conventional D2 can reach 63/65 it isn't unreasonable to expect a finer carbide dispersion to get 1-2 points more.

-Cliff
 
Cliff Stamp said:
No you would still temper, 325-375C or so. Yes the grindability would be low, more so due to the carbide than the hardness. But this should not be a factor in use of the knife given proper suitability to the tasks of the blade and geometry. Since conventional D2 can reach 63/65 it isn't unreasonable to expect a finer carbide dispersion to get 1-2 points more.

-Cliff
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well if it does come out that high, it will be interesting to see how the edge toughness holds up.
 
Cliff, I recently got some more information on the process and testing. The material is D2 and the claim is very fine grain size and high hardness
(67). No question this combination would be a great cutter. There was some discussion on toughness but no test results on Charpy values or other discussion on dynamic toughness, just a bending test with the hard cutting surface (1/2 inch wide) and the rest of the blade at close to annealed hardness. They compared the RC 67 D2 test blade against a S-90V and S30V test blade with the same geometry. The S0V compared best. The new process D2 blade out lasted the S90V. They claim the S90V hardness at 59-62. In my experience it is difficult to get S90V above 60 with reasonable toughness. So the comparison is a blade of RC 67 against a blade of 60 or less. Again my experience is that hardness makes a big difference when cutting abrasive materials. I guess I can conclude from this limited information that if the new process D2 has reasonable toughness at 67 then this is great performance. I will try to get a little more info.. PHIL
 
I got the same info that Phil has a while back, the cutting tests they were doing were stuff that Cliff would like much more.
 
Phil Wilson said:
... a bending test with the hard cutting surface (1/2 inch wide) and the rest of the blade at close to annealed hardness.
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That is a kind of critical point to not advertize as then all you are bending is a small strip of steel. You can bend M2 at 66 HRC to 180 degrees easily in a bi-metal hacksaw blade. They of course know that if they don't say anything that everyone assumes a full hard blade.

The problem with the Crucible steels is that they are too focused on carbide content at the expense of hardness. This will give excellent long term edge retention at a low sharpness, but to keep the initial crisp edge and have high sharpenability you want a high hardness.

-Cliff
 
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