Some More ?'s About FF D2

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me2

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Oct 11, 2003
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I have a few more, kinda technical, questions about Friction Forged D2 that I didnt see the answers for on the website or other threads. Hopefully, cds4byu will chime in, since he helped develop it, but I didnt want to address them specifically to him, since some of the knives are out and user feedback would be appreciated also.

1.) According to the web site, the steel hardens after the friction mandrel makes its pass. Is any tempering done afterward? If so, how much, if its not proprietary.

2.) Also according to the web site, the FF area is heated to a temperature high enough to disolve enough Cr that the edge area is stainless. Does this mean that 11.5 - 12% Cr is in solution?
a.) If so, is the volume of carbides reduced well below what is normal for D2?
b.) If so, then is the exceptionally high hardness primarily responsible for the high edge holding?

3.) I read the article years ago on friction stir welding aluminum and steel. The intermetallic that forms between these 2 is reduced, and broken up and well dispursed so that it doesnt cause near as much trouble as in arc welded Al and steel. Does the same thing apply to the carbides in FF D2?

4.) Are there any reports of edge toughness issues among users, given the unusually high hardness?
 
I seem to have posted this in the wrong area. Please move it to the testing forum if that is more appropriate.
 
me2 said:
I have a few more, kinda technical, questions about Friction Forged D2 that I didnt see the answers for on the website or other threads. Hopefully, cds4byu will chime in, since he helped develop it, but I didnt want to address them specifically to him, since some of the knives are out and user feedback would be appreciated also.

1.) According to the web site, the steel hardens after the friction mandrel makes its pass. Is any tempering done afterward? If so, how much, if its not proprietary.

2.) Also according to the web site, the FF area is heated to a temperature high enough to disolve enough Cr that the edge area is stainless. Does this mean that 11.5 - 12% Cr is in solution?
a.) If so, is the volume of carbides reduced well below what is normal for D2?
b.) If so, then is the exceptionally high hardness primarily responsible for the high edge holding?

3.) I read the article years ago on friction stir welding aluminum and steel. The intermetallic that forms between these 2 is reduced, and broken up and well dispursed so that it doesnt cause near as much trouble as in arc welded Al and steel. Does the same thing apply to the carbides in FF D2?

4.) Are there any reports of edge toughness issues among users, given the unusually high hardness?
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Me2,

1. there is no post process tempering performed.

2. Yes, this implies that there is roughly 12% Cr in solution in the FF processed region. We have performed some corrosion tests in salt water and the processed region shows no signs of corrosion even after several weeks.

2a. Yes, FF does reduce the volume fraction of carbides. I do not have an exact number yet. We are presently working on quantifying this.

2b. Yes, The edge holding capabilities of the FF blades is due to the increased hardness. The very high hardness is produce by both the increase alloy content in the martensitic matrix, and the extremely fine grain size.

At these hardness values, most knife steels would not be very functional due to poor ductility/toughness. In the FF D2 the changes in microstructure have improved the toughness resulting in a function knife at Rc 65-68.

3. The carbides are broken up and more uniformly distributed in the FF D2.

4. No user reports of toughness issues. Our preliminary test indicate that FF D2 at 66-68 has very good toughness. This was assessed with chopping test on different materials.

Hope this helps,

Tracy
 
"4. No user reports of toughness issues. Our preliminary test indicate that FF D2 at 66-68 has very good toughness. This was assessed with chopping test on different materials."

Aside from the very fine grain size and the fine carbide dispursion, are there any other microstructural features that contribute to toughness? Certainly these 2 should be enough, but just wondering. I have seen bridge plate double its impact values in Charpy V notch testing at reduced temperatures based on improved (finer) grain size.

When you say good toughness, is that compared to regular D2, other cutlery steels at these high hardness levels, cutlery steels in general, or other steels, like structural steels? With such a fine grain size, I would love to see the toughness of a 1055 or 5160 blade. It may have been covered in one of the other threads, but what materials were chopped? Wood, Micarta, metals?

Anyway, thanks for the reply.
 
Lanza said:
What is the preferred sharpening method on this steel?
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Lanza,

I am trying to replicate Wayne Goddard's sharpening technique. He demonstrated that the FF knives are relatively easy to sharpen with the Norton Crystalon (??) followed by a fine India stone.

Tracy

me2 said:
"4. No user reports of toughness issues. Our preliminary test indicate that FF D2 at 66-68 has very good toughness. This was assessed with chopping test on different materials."

Aside from the very fine grain size and the fine carbide dispursion, are there any other microstructural features that contribute to toughness? Certainly these 2 should be enough, but just wondering. I have seen bridge plate double its impact values in Charpy V notch testing at reduced temperatures based on improved (finer) grain size.

When you say good toughness, is that compared to regular D2, other cutlery steels at these high hardness levels, cutlery steels in general, or other steels, like structural steels? With such a fine grain size, I would love to see the toughness of a 1055 or 5160 blade. It may have been covered in one of the other threads, but what materials were chopped? Wood, Micarta, metals?

Anyway, thanks for the reply.
Click to expand...

Me2,

At this point I can not say if there are any other contributors to the improved toughness at these hardness values. We are currently investigating this and hope to report on it by the first of the year. At this point, I am confident in stating that the increase in toughness is mostly the result of the very fine grain size and the smaller average carbide size.

With regards to toughness: Yes, I was comparing this to traditional D2 at 59-60. I don't feel that other cutlery steels at Rc 65-68 would perform well at all under chopping conditions.

With regards to the chopping test: These qualitative tests were performed on desert iron wood, antler, bone, then a brick and finally a steel anvil. These were done with a blade designed more for chopping, e.g. larger included angle on the final edge. The knives currently being sold by DiamondBlade are not designed for chopping, but for skinning and capping.

Regards,

Tracy
 
Are there any industrial applications in which FF D2 is being used/tested?
 
Can you comment on how the toughness compares to a fine grained low carbide steel, such as 1095 or O1 at the 64-66 level with a grain size of 2-3 microns, which IIRC, is about a 14-15 on the ASTM scale?
 
You only need like 10% chromium in solution to be stainless, even 9%, there isn't really a number that is set in stone. D2 is well under 9% normally though.
 
All I know is, my FFD2 Goddard kicks ass ref. taking the backstraps out of a deer...the hair and flesh seem to pop apart even before the blade touches it. :thumbup:
 
Troop said:
All I know is, my FFD2 Goddard kicks ass ref. taking the backstraps out of a deer...the hair and flesh seem to pop apart even before the blade touches it. :thumbup:
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Can it split the hair this way?

hair-08.jpg


Now with only few having this knives and price for tiny little one for $400 it is pretty strange argument - "no user complain about toughness". I can imagine someone who bought this little knife for $400 start chopping wood or trying to break it. Plus how long this users may have this knives - few monthes most I guess.

I rather see some test data on this (toughness).

Thanks, Vassili.
 
From the earlier posts by T. Nelson, there is still quite a bit of R&D going on, such as quantifiying carbide volume percentage and more microscopy.

Regarding Cr content for stainlessness, I read an article by Ed Severson in Blade years ago that gave a number at 11.5% in solution to be considered "stainless." Even if thats not it, there is a value somewhere that marks the cutoff. It is true that increasing Cr from 0%-10% reduces corrosion in certain environments, its just that at 10%-15% there is a plateau that marks the "stainless" steels.
 
me2 said:
From the earlier posts by T. Nelson, there is still quite a bit of R&D going on, such as quantifiying carbide volume percentage and more microscopy.

Regarding Cr content for stainlessness, I read an article by Ed Severson in Blade years ago that gave a number at 11.5% in solution to be considered "stainless." Even if thats not it, there is a value somewhere that marks the cutoff. It is true that increasing Cr from 0%-10% reduces corrosion in certain environments, its just that at 10%-15% there is a plateau that marks the "stainless" steels.
Click to expand...

When I started college a couple of decades ago, 10-12% Cr was the standard stainless range. Then in the late 80s, 11-11.5% Cr became the practice. In the 90's, the standard became 12%Cr minimum to be considered Stainless steel. 12%Cr is what is quoted in all the standards and technical literature now.

I agree with Larin in that you can get some stainless benefits with even 9%Cr as long as the environment is not too harsh, e.g. rain versus prolonged humidity or salt water.

I believe the AISI and ASTM standards state that the range Cr in D2 is suppose to be 11-13%Cr. Of course, not all of the Cr is in solution otherwise D2 would be "stainless". some fraction of the Cr is ties up in Cr carbides, reducing the amount in solution.

Troop said:
All I know is, my FFD2 Goddard kicks ass ref. taking the backstraps out of a deer...the hair and flesh seem to pop apart even before the blade touches it. :thumbup:
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Troop,

Glad to hear you finally used that knife.

nozh2002 said:
Can it split the hair this way?

Thanks, Vassili.
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Vassili,

I haven't looked that close, but is takes the hair off my arm without pressing the blade against the skin.

me2 said:
Can you comment on how the toughness compares to a fine grained low carbide steel, such as 1095 or O1 at the 64-66 level with a grain size of 2-3 microns, which IIRC, is about a 14-15 on the ASTM scale?
Click to expand...

Not quantitatively yet.

Good to hear from everyone,

Tracy
 
tnelson said:
I haven't looked that close, but is takes the hair off my arm without pressing the blade against the skin.
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It takes 40 grams weight to cat thin cotton thread (median on 21 tests) or split hair like this.

It is very easy to do it yourself. To reproduce it take your hair off your head and try to slice it from top to bottom - you may notice hair start bouncing when edge (if it thin enough) hit hair scales and at some point it starts shaving it.

Hair scales are oriented lik on palm tree so it is important to go from top to bottom, so if you pull hair from your head - just keep it the way thay take off...

Thanks, Vassili.
 
One thing I like about the FF knives I have seen so far has nothing to do with the blade steel and everything to do with the beautiful classic designs with great natural handle material. I would be interested even without the edge retention bonus.
 
Unsub said:
One thing I like about the FF knives I have seen so far has nothing to do with the blade steel and everything to do with the beautiful classic designs with great natural handle material. I would be interested even without the edge retention bonus.
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I rather prefer something simple and basic to make it more affordable. Current price is just too high. I am interested in this technology and will to get just an unpolished blade without handle if it make this affordable. I can make handle myself, but unfortunately it is impossible - I called them already.

Thanks, Vassili.
 
nozh2002 said:
I rather prefer something simple and basic to make it more affordable. Current price is just too high. I am interested in this technology and will to get just an unpolished blade without handle if it make this affordable. I can make handle myself, but unfortunately it is impossible - I called them already.

Thanks, Vassili.
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Ah, Comrade....I KNEW you wanted one! :D:D:D
 
Troop said:
Ah, Comrade....I KNEW you wanted one! :D:D:D
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Well being called by Sal as steel juncky and having almost any steel available used for knives and bulat, of course I want one, but it is just too expensive. I also want YXR7 and Balbah damascus, but it is also too expensive...

But will you split the hair first?

Thanks, Vassili.
 
nozh2002 said:
Well being called by Sal as steel juncky and having almost any steel available used for knives and bulat, of course I want one, but it is just too expensive. I also want YXR7 and Balbah damascus, but it is also too expensive...

But will you split the hair first?

Thanks, Vassili.
Click to expand...
Do I get to put the magic touch on the edge? Or, do you want this to be a FFD2 factory-edge challenge? :)
 
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