Friction Forged Blades : CATRA tests

[gator68]

The back is tempered martensite.

Carl

Thanks for the information. I'm still curious about the desire to have such a soft back. I've never had a blade break on me, despite doing some *bad* things in my life. But then I've never messed around with a large D2 blade.

Is the company really concerned about a hunter made from D2 breaking? Bob Dozier makes tons of D2 blades, and I don't think he does any differential tempering on his.

 

[Kohai999]

Thanks for the information. I'm still curious about the desire to have such a soft back. I've never had a blade break on me, despite doing some *bad* things in my life. But then I've never messed around with a large D2 blade.

Is the company really concerned about a hunter made from D2 breaking? Bob Dozier makes tons of D2 blades, and I don't think he does any differential tempering on his.

Dozier uses fairly thick stock, at least 1/8", with the larger blades around 3/16". It makes a difference.

Best Regards,

STeven Garsson

 

[gator68]

Dozier uses fairly thick stock, at least 1/8", with the larger blades around 3/16". It makes a difference.

Best Regards,

STeven Garsson

I haven't seen stats on the FFD2 blades. What's the thickness of these blades? Is there a website set up yet for the company?

edit: I guess the site will be www.diamondbladeknives.com. But it's not up yet, and I haven't seen pics or stats for any of the knives.

 

[hardheart]

I'm not proposing that L6 is a great knife steel, but it's a steel I have this data for. If I were making a knife out of L6, I certainly wouldn't want to go harder than HRC62, because the toughness gets too low. And if I were making a machete out of L6, then I might even keep the hardness down to 57, because the toughness is much higher.

isn't it still a whole lot tougher than most stainless steels, as well as traditional D2?

 

[gator68]

isn't it still a whole lot tougher than most stainless steels, as well as traditional D2?

Good point, Crucible lists D2 as having a toughness of 21 ft-lbs at HRc = 60. Much less than the L6 curve shown.
D2 datasheet

 

[Kohai999]

isn't it still a whole lot tougher than most stainless steels, as well as traditional D2?

L6 is generally used for larger blades and swords. It IS plenty tough. It is also very rust prone, and the reason that the cutlery industry likes D2 is that the amount of chromium contained reduces rusting quite a bit.

When you are starting a new cutlery business, launching with a carbon steel will automatically reduce access to the intended consumer base.

Best Regards,

STeven Garsson

 

[Cliff Stamp]

Is the company really concerned about a hunter made from D2 breaking? Bob Dozier makes tons of D2 blades, and I don't think he does any differential tempering on his.

Few people do as it is air hardening. A. G. Russell makes the Deerhunter out of D2, it is 1/16" stock. Unless you are impacting the spine of your hunter with a rock all you did was make a weaker blade. It will take a set with LESS force.

All steels, regardless of the alloy, will be stronger as they are harder. Stronger means that it will take more force to permanently deform them. At the same time, all steels will be less tough as they are harder. Less tough means that cracks will run through them more easily.

Impact toughness isn't monotonic in this manner and neither is strength, especially for knife edges.

About 15 or so years ago the knife-list was polled asking makers which steel would they use for themselves.

L6 was the most common answer.

-Cliff

 

[kneedeep]

Carl, thanks for the great (and very informative) answer. I feel like I am learning something.

 

[cds4byu]

Impact toughness isn't monotonic in this manner and neither is strength, especially for knife edges.
-Cliff

Of course toughness isn't monotonic with hardness. The plot I showed on L6 clearly shows that. But it's certainly a general trend.

Hardness is proportional to strength, when you're talking about the material property, specifically yield strength.

Edge strength isn't a material property, it's a property of a blade, so it doesn't have to follow with hardness. But it's still generally true, in my experience.

Carl

 

[cds4byu]

isn't it still a whole lot tougher than most stainless steels, as well as traditional D2?

Apparently so. I wasn't proposing it as not a great knife steel either. I was making no recommendation either way. I was just showing the data, because I had it in my tool steels handbook.

Carl

 

[Cliff Stamp]

There are a number of regions in cutlery steels where these quantities deviate from monotonic significantly, 500F and 950F specifically are toughness critical points. The big problem with general trends are not specifying the criteria, so for example is D2 at 55 HRC tougher than S7 at 59 HRC. Even strength can be higher at a lower hardness, specifically compressional strength in very high carbide steels. The problem with general trends is that they get accepted as laws with no reservations, you see this all the time if you read the forums.

-Cliff

 

[Broos]

The problem with general trends is that they get accepted as laws with no reservations, you see this all the time if you read the forums.

-Cliff

Yeah, I saw a thread about edge retention where some guy is doing that.

 

[cds4byu]

The big problem with general trends are not specifying the criteria, so for example is D2 at 55 HRC tougher than S7 at 59 HRC.
-Cliff

Apparently I was not clear in my statement. I said that for a particular steel, when you make it harder, you make it less tough. Nothing in statement should be used to compare different steels. You can't make any kind of blanket statement about steels in general, that says if steel A is harder than steel B, then steel A will be less tough than steel B.

If I was unclear, I apologize. I hope I have clarified any misunderstanding.

Carl

 

[ernestrome]

It it possible that we could ff an entire blade, but probably not cost effective.

It is also possible to FSW/FF a high-performance edge to a stainless back. We have done this in the laboratory, but can't yet do it in a production-ready manner. It's on the table for future research.

My personal opinion is that we can find a stainless alloy that will be provide an FF edge of quality similar to or better than FFD2. That's also on the future table.

All of this future work will take place once the generation 1 knives are on the market.

Carl

Very interesting, thanks.

 

[insector]

I agree...let the smart guys take up the literature and lets get this stuff into the field...we'll just need to wait. Everyone wants to change the world but I have heard of magic bullets before and time will tell. Thanks for the info...

 

[M Wadel]

now we´re talking..

however i think it will be hard to FF Ti-blades. first the Ti starts oxidize (if that the correct word?) at about 400°C or so iirc, so it would probably have to be in a controlled atmosphere?

and then there is the galling, Ti sticks to tools, which causes overheating (i don´t know if this will lower the performance of the Ti). titanium is very elastic and generally pretty hard/expensive to machine, needs cooling, i would´nt know how to get around these "problems"?

i´ve machined some Ti and it needs very low revs/high feed/much cooling/cutting fluid not to overheat and melt the tools. but as i read in this thread, it can be done with tungstencarbide tools so it might not be a problem.




but maybe the scientists can get around these problems, i would definitely buy a Ti-blade at 58hrc+ any day. could it be done at a reasonable price?

edit:about the FFD2: i saw you could get grainsize down to 80nm, why is 500nm preferred? would´nt 80nm be even better?

 

[tnelson]

now we´re talking..

however i think it will be hard to FF Ti-blades. first the Ti starts oxidize (if that the correct word?) at about 400°C or so iirc, so it would probably have to be in a controlled atmosphere?

and then there is the galling, Ti sticks to tools, which causes overheating (i don´t know if this will lower the performance of the Ti). titanium is very elastic and generally pretty hard/expensive to machine, needs cooling, i would´nt know how to get around these "problems"?

i´ve machined some Ti and it needs very low revs/high feed/much cooling/cutting fluid not to overheat and melt the tools. but as i read in this thread, it can be done with tungstencarbide tools so it might not be a problem.




but maybe the scientists can get around these problems, i would definitely buy a Ti-blade at 58hrc+ any day. could it be done at a reasonable price?

M Wadel,

Ti would be more difficult due to oxidation and tooling. It can be done. Anthony Reynolds has process Ti for super plasticity purposes. It was done in collaboration with some researchers in Israel. I do not think the results were published. In regards to knives, I don't think we would see as much an improvement as we see in D2.

edit:about the FFD2: i saw you could get grainsize down to 80nm, why is 500nm preferred? would´nt 80nm be even better?

We can achieve grain sizes less than 100 nm in aluminum and copper, but the procedure is not very conducive to a manufacturing environment yet.

We can consistently get 400-800 nm very easily in D2 by varying the rotational and travel speeds. We have not put a significant effort into trying to achieve grain sizes below 400nm in D2. Future work.

TN

 

[M Wadel]

great answer. thanks

i had a feeling Ti would´nt respond as good as steel, but i´m looking forward to see what other FF steels and materials will show in the future.

 

[Cobalt]

While I understand your meaning, we have to be clear.

INFI is a steel. FFD2 is a process. It doesn't seem that anyone is calling DiamondBlade knives a different steel, just that it is subjected to a process that makes very desireable changes in it.

It is MUCH easier to farm out a steel, than it is a process for working it. Jerry Busse controls the steel very closely, but he HAS let some pieces of it out for custom makers.

Best Regards,

STeven Garsson

Actually my understanding is that INFI is a steel and process combination, hence, the reason why only finished stock has ever been handed out to a few knifemakers.

In other words you could not do an elemental analysis of it and go to some steel maker and duplicate the steel without knowng the secret of the process. Because if that was the case, INFI would no longer be a secret.

I guess the CPM steels are also a "process and steel" as the only way to get such a homogenous steel is by their process. You could not recreate S30V, S90V, etc. by anything other than their process if I am not mistaken.

so FF D2 is anothr process and steel, since the process was honed for that steel as of this moment.

 

[Kohai999]

Actually my understanding is that INFI is a steel and process combination, hence, the reason why only finished stock has ever been handed out to a few knifemakers.

In other words you could not do an elemental analysis of it and go to some steel maker and duplicate the steel without knowng the secret of the process. Because if that was the case, INFI would no longer be a secret.

I guess the CPM steels are also a "process and steel" as the only way to get such a homogenous steel is by their process. You could not recreate S30V, S90V, etc. by anything other than their process if I am not mistaken.

so FF D2 is anothr process and steel, since the process was honed for that steel as of this moment.

It is my understanding that Jerry hands out blanks to makers, and then Busse Knives does the heat treat on the completed blades.

I stand by what I said.......FF is a process that differs from heat treating, and CPM is certainly a different process than heat treating, it is a WAY of MANUFACTURING steel.

AFAIK, the BYU boys started out with regular, off the shelf D2. There is no such thing as regular off the shelf INFI, it is only available though Busse Knife Company.

Best Regards,

STeven Garsson