Sintered Metals & Ceramics: Possibly In Spyderco's Future?

[Cliff Stamp]

Or do any of you know about current studies or advances in Sintered materials.

There is strong interest in ceramics because of the extreme properties they have (temperature resistance, wear resistance, stiffness, strength, etc.). The main problem they have is just brittleness compared to steels. Anyone who has used one of the older ceramic blades has seen how they can be broken under impacts which are trivial compared to steels.

However, and this is a big however, modern reinforcement of ceramics is literally exploding the paradigm of toughness. One of the main ways this is gained is through transformation toughening. This is similar to work hardening in steels. When the ceramic comes under a load and starts to crack this crack actually causes change in the ceramic which inhhibit crack growth (r-curve behavior).

A few papers :

-r-curve utilization : http://www2.lbl.gov/ritchie/Library/PDF ... ramics.pdf" target="_blank

-review of high toughness ceramic for cutting tools : http://www.journalamme.org/papers_vol54_2/5427.pdf" target="_blank

-commercial data sheet : http://www.360ip-japan.com/uploads/docs ... ummary.pdf" target="_blank

The last one is similar to a data sheet from Bohler or similar, it isn't a peer reviewed source so look at it as basically a claim. However it does show the potential for extreme toughness in ceramics, just look at how high the toughness is claimed compared to standard high-toughness ceramics.

As more of a source of entertainment, a reality show which runs a traditional knifemaker vs a engineering team which eventually uses a carbide blade (this is a sintered product) :

https://youtu.be/UyCuR16HUBc" target="_blank

The big problem to over come using these as traditional knife steels is mainly sharpening. They do not sharpen well on most stones, you need CBN or diamond to work them and burr-sharpening doesn't work. However if you are not reliant on burr methods and you micro-bevel they are not that problematic to work. The only thing I have not been able to figure out is how to get an aggressive low-grit slicing edge on them, they seem to tend to be abraded mainly by fracture (steel will deform) and thus they really only get really sharp under high polishes.

[Bill1170]

Or do any of you know about current studies or advances in Sintered materials.

There is strong interest in ceramics because of the extreme properties they have (temperature resistance, wear resistance, stiffness, strength, etc.). The main problem they have is just brittleness compared to steels. Anyone who has used one of the older ceramic blades has seen how they can be broken under impacts which are trivial compared to steels.

However, and this is a big however, modern reinforcement of ceramics is literally exploding the paradigm of toughness. One of the main ways this is gained is through transformation toughening. This is similar to work hardening in steels. When the ceramic comes under a load and starts to crack this crack actually causes change in the ceramic which inhhibit crack growth (r-curve behavior).

A few papers :

-r-curve utilization : http://www2.lbl.gov/ritchie/Library/PDF ... ramics.pdf" target="_blank

-review of high toughness ceramic for cutting tools : http://www.journalamme.org/papers_vol54_2/5427.pdf" target="_blank

-commercial data sheet : http://www.360ip-japan.com/uploads/docs ... ummary.pdf" target="_blank

The last one is similar to a data sheet from Bohler or similar, it isn't a peer reviewed source so look at it as basically a claim. However it does show the potential for extreme toughness in ceramics, just look at how high the toughness is claimed compared to standard high-toughness ceramics.

As more of a source of entertainment, a reality show which runs a traditional knifemaker vs a engineering team which eventually uses a carbide blade (this is a sintered product) :

https://youtu.be/UyCuR16HUBc" target="_blank

The big problem to over come using these as traditional knife steels is mainly sharpening. They do not sharpen well on most stones, you need CBN or diamond to work them and burr-sharpening doesn't work. However if you are not reliant on burr methods and you micro-bevel they are not that problematic to work. The only thing I have not been able to figure out is how to get an aggressive low-grit slicing edge on them, they seem to tend to be abraded mainly by fracture (steel will deform) and thus they really only get really sharp under high polishes.

Because of their propensity for fracturing, even if you could produce a low-grit aggressive finish, it seems that it would crumble in use, leaving particles of ceramic in whatever was being cut. Isn't an aggressive finish just a serrated edge at a micro scale? It is pretty clear that with macroscopic serrations, tougher steels hold up best, resisting fracture of the points.

[SpyderEdgeForever]

There was a nanotechnology researcher who came up with a possible way to combine the pros of hard, brittle materials, while making them tough and elastic. This was some of the text from their presentation:

" There are a number of problems with forming single crystal macro-sized structural members. One of the foremost is getting the crystals to be large enough and the correct shape. Various methods have been used to get around this problem, such as growing crystals the same way that semiconductor crystals are made, or by sintering, as is the case with tungsten carbide. Unfortunately, there are problems associated both with the manufacturing techniques and with the resulting materials. In the case of tungsten carbide and similar materials, extreme hardness can be achieved but at the result of extreme brittleness. This is made even more apparent as a result of case and surface hardening techniques applied to various steels. While the techniques can be used, they are still not perfect and can result in overly brittle or otherwise defective or limited materials. The use of carbon nanotubes for extreme longitudinal strength is used to overcome one of the major problems of single crystal macro-sized strength members; to wit, the difficulty in forming flawless crystals of the requisite size and shape. The crystal structures provide tremendous shearing and compressive strength while the nanotubes provide longditudinal strength, resulting in uniquely strong and durable materials without the attendant brittleness and other effects previously encountered in single-crystal materials.

Another problem with extremely aligned and single-crystal materials is that, in the case of steels, one will end up with a really powerful magnet, since in a single crystal all of the magnetic domains are lined up and reinforcing each other. In the case of nanotube-reinforced structures, the crystal shapes can be chosen so that the magnetic domains are not aligned, resulting in a magnetically neutral structure.

We will present several possible overall structures and crystal structures, and also discuss manufacturing methods.

This presentation describes the engineering problems associated with the use of nanotech-scale modules to form large-scale structural members.

The design of the individual modules includes provision for each module to know the positions of any module in contact. This will allow the overall structural member to be rebuilt automatically if part of it is damaged or torn away, allowing repair to be very easy and quick. Given that the resulting structures are strong enough, the application for such things as self-sharpening knife blades and tool bits is obvious.

By altering the way in which individual modules are linked together, one can create structures that range in rigidity from extremely so to very flexible. Since these structures are active in nature, they will have abilities not possessed by the equivalent conventional materials; for example, very thin yet rigid walls with active sound cancelling capabilities to allow for extremely efficient soundproofing. Two layers separated by evenly spaced supports with a vacuum between them would provide extremely effective heat and cold insulation.

By changing the characteristics of the links after the structure has been formed, and, more importantly, by changing the pattern of the links, it would be possible and practical to create mutable tools. For example, programming the modules one way creates a hammer, another way creates a screwdriver, yet another a saw. The technique can also be used, in an advanced form, to create customized tools on the fly, for example, a wrench that can reach through a tangle of wires and pipes, form itself around a nut and then act as a motorized socket wrench that fits the nut exactly and won't slip.

This presentation addresses the practical engineering problems associated with such materials, and describes a design that is capable of implementing the above features. We also suggest several manufacturing scenarios.

Sadly, I found out, the person who was pursuing this line of research died suddenly of a physical condition. What a loss to humanity =(

[Cliff Stamp]

It is pretty clear that with macroscopic serrations, tougher steels hold up best, resisting fracture of the points.

This is where it gets sort of interesting. If you take for example something like :

10V vs AEB-L

and do a bunch of slicing on ropes, cardboard etc. then the advantage goes to 10V significantly when you cut to low sharpness -and- the material can fracture the edge which leaves a very jagged sharpness. If the steel is really tough and just tends to wear smooth it just evens out. Ideally you want apex to behave like a grinding wheel and break apart and keep presenting sharp surfaces if you are slicing, but if you are push cutting you don't want that at all.

Here is an O1 blade blunted :



See how the apex is mainly smooth with one irregular spot in the middle (the white part) which is mainly deformation. In contrast here is a 121REX blade :



It blunts by micro-chipping.

Now which of these has better edge retention? It depends on if you are push cutting or slicing, and how much load you are applying. If you are applying a heavy load (cutting with a semi-sharp/blunt blade) and slicing then the 121REX has better edge retention. If you are cutting with a low load (sharp blade) and/or push cutting the O1 does better.

I keep meaning to spend some serious times on ceramics and sharpening. I just got a heavily damaged set of DMT 12" stones so there is a decent experiment anyway.

[Cliff Stamp]

There was a nanotechnology researcher who came up with a possible way to combine the pros of hard, brittle materials, while making them tough and elastic.

http://foresight.org/Conference/MNT10/A ... index.html" target="_blank

All of this research, or at least a large part of it, is heavily computer modeled. I remember back in olden times when a 386 was a fast processor. I was doing heavily numeric processing at the time when new pentium processors came in. All of a sudden we could do in hours what used to take days. It opened up experiments that were simply not possible previously.

As computers keep advancing our ability to do extremely intricate manipulations do so as well.

Imagine something like a blade steel which has the properties of a basic 0.6% carbon steel, extremely tough and strong, but reacts under wear to form extremely hard/wear resistant structures right at the apex of a knife. To make a steel which behaves just like that isn't going to be that far from fantasy given the kinds of things we know now and our growing ability to manipulate materials.

[Ankerson]

There was a nanotechnology researcher who came up with a possible way to combine the pros of hard, brittle materials, while making them tough and elastic. This was some of the text from their presentation:

" There are a number of problems with forming single crystal macro-sized structural members. One of the foremost is getting the crystals to be large enough and the correct shape. Various methods have been used to get around this problem, such as growing crystals the same way that semiconductor crystals are made, or by sintering, as is the case with tungsten carbide. Unfortunately, there are problems associated both with the manufacturing techniques and with the resulting materials. In the case of tungsten carbide and similar materials, extreme hardness can be achieved but at the result of extreme brittleness. This is made even more apparent as a result of case and surface hardening techniques applied to various steels. While the techniques can be used, they are still not perfect and can result in overly brittle or otherwise defective or limited materials. The use of carbon nanotubes for extreme longitudinal strength is used to overcome one of the major problems of single crystal macro-sized strength members; to wit, the difficulty in forming flawless crystals of the requisite size and shape. The crystal structures provide tremendous shearing and compressive strength while the nanotubes provide longditudinal strength, resulting in uniquely strong and durable materials without the attendant brittleness and other effects previously encountered in single-crystal materials.

Another problem with extremely aligned and single-crystal materials is that, in the case of steels, one will end up with a really powerful magnet, since in a single crystal all of the magnetic domains are lined up and reinforcing each other. In the case of nanotube-reinforced structures, the crystal shapes can be chosen so that the magnetic domains are not aligned, resulting in a magnetically neutral structure.

We will present several possible overall structures and crystal structures, and also discuss manufacturing methods.

This presentation describes the engineering problems associated with the use of nanotech-scale modules to form large-scale structural members.

The design of the individual modules includes provision for each module to know the positions of any module in contact. This will allow the overall structural member to be rebuilt automatically if part of it is damaged or torn away, allowing repair to be very easy and quick. Given that the resulting structures are strong enough, the application for such things as self-sharpening knife blades and tool bits is obvious.

By altering the way in which individual modules are linked together, one can create structures that range in rigidity from extremely so to very flexible. Since these structures are active in nature, they will have abilities not possessed by the equivalent conventional materials; for example, very thin yet rigid walls with active sound cancelling capabilities to allow for extremely efficient soundproofing. Two layers separated by evenly spaced supports with a vacuum between them would provide extremely effective heat and cold insulation.

By changing the characteristics of the links after the structure has been formed, and, more importantly, by changing the pattern of the links, it would be possible and practical to create mutable tools. For example, programming the modules one way creates a hammer, another way creates a screwdriver, yet another a saw. The technique can also be used, in an advanced form, to create customized tools on the fly, for example, a wrench that can reach through a tangle of wires and pipes, form itself around a nut and then act as a motorized socket wrench that fits the nut exactly and won't slip.

This presentation addresses the practical engineering problems associated with such materials, and describes a design that is capable of implementing the above features. We also suggest several manufacturing scenarios.

Sadly, I found out, the person who was pursuing this line of research died suddenly of a physical condition. What a loss to humanity =(

Look at Super Bainite, now that is some amazing stuff for what it's being developed for.

http://www.army-technology.com/features ... y-4346392/" target="_blank

But then the Military and Aerospace industry will always be on the cutting edge of development for obvious reasons.

[Bill1170]

It is pretty clear that with macroscopic serrations, tougher steels hold up best, resisting fracture of the points.

This is where it gets sort of interesting. If you take for example something like :

10V vs AEB-L

and do a bunch of slicing on ropes, cardboard etc. then the advantage goes to 10V significantly when you cut to low sharpness -and- the material can fracture the edge which leaves a very jagged sharpness. If the steel is really tough and just tends to wear smooth it just evens out. Ideally you want apex to behave like a grinding wheel and break apart and keep presenting sharp surfaces if you are slicing, but if you are push cutting you don't want that at all.

Here is an O1 blade blunted :



See how the apex is mainly smooth with one irregular spot in the middle (the white part) which is mainly deformation. In contrast here is a 121REX blade :



It blunts by micro-chipping.

Now which of these has better edge retention? It depends on if you are push cutting or slicing, and how much load you are applying. If you are applying a heavy load (cutting with a semi-sharp/blunt blade) and slicing then the 121REX has better edge retention. If you are cutting with a low load (sharp blade) and/or push cutting the O1 does better.

I keep meaning to spend some serious times on ceramics and sharpening. I just got a heavily damaged set of DMT 12" stones so there is a decent experiment anyway.

Yes, I get all that about fresh edges exposed by fracture being useful in a draw cut. I guess it is a question of crumble rate combined with the form the apex takes as it crumbles.

The ideal edge would self sharpen. Sadly, what we usually see is the apex becomes a plateau whose width grows wider at a rate that gets slower as the blunting proceeds. If a rough edge holds up a long time, it'll tear through media a long time. If that rough edge fails by massive fracture in a short time, then it quickly loses its utility. So the rate of crumble affects useful life.

In bench stones we can tolerate high friability because it is a flat surface on the macro level, with less need to hold its exact shape to do the job, and a friable stone oftens cuts faster due to the fresh grains being exposed all the time. But a Crystolon knife blade would become useless for slicing in short order due to the high rate of crumbling. I realize that a TTZ blade crumbles slower than a Crystolon stone, but my limited experience with TTZ blades was frustrating because of chipping even under careful use.

[Cliff Stamp]

But a Crystolon knife blade would become useless for slicing in short order due to the high rate of crumbling. I realize that a TTZ blade crumbles slower than a Crystolon stone, but my limited experience with TTZ blades was frustrating because of chipping even under careful use.

Silicon carbide stones don't actually have to be very friable, they often are by design, but if they have a very strong vitrified bond they won't. They often have soft bonds as they are used for roughing while aluminum oxide stones are generally for finishing.

I would not advocate ceramics for superior edge retention in coarse edges, as noted, I can not even get decent behavior with them sharpness wise, just making a point that lack of toughness in general isn't always a detriment for edge retention.

One thing to keep in mind is that often the ceramics we see in knife blades are very basic ceramics, the equivalent of mild steel being used in knives. The problem is that even basic ceramics work amazingly well for a lot of people.

However the new ceramics with finer crystal size may make interesting knife blades, it will just take a maker/manufacturer who is willing to experiment with them.

[SolidState]

It is probably the most insulting thing that someone can do.

That's the internet, have you not seen how often people will reject metallurgical data, and just sweep science aside when discussing steels, heat treatments and knives?

It is the antithesis of scientific morality.

I think there is a leap here as you are presenting two extreme ends of the spectrum.There is a large difference between an overly passionate fan and someone intentionally spreading misinformation for some self-serving purpose. Here is the thing, you know your conclusions are justified because of work you have done, but how does anyone else know yours are justified and something else that someone else claimed isn't? Not everyone can put in the foundational work to separate it out on a basic level by looking at the methodology.

Thanks for the reminder, and also for the extreme reach at the end of the post. I am aware of the work of Dunning and Kruger. I will link the paper - as it is really the only piece of science needed to respond to your critique.
http://gagne.homedns.org/~tgagne/contrib/unskilled.html" target="_blank

You are right though, pointing to tens of years of experience is not a valid reason for anything. ****, knowing the vocabulary and being able to actually read the methods isn't worth anything either. As you said "That's the internet."

Also, to be clear, I am not insulted in the least by Cliff's posts directed toward me. I honestly find them to be most reminiscent of the professional discourse I am used to in my field. He writes no differently than most of the engineers and scientists I work with. That said, I'm not impressed by his addition of fuel to the pseudoscience fire. Believe me, I would have posted articles about nanobots to refute the ridiculous claims of others in the post if any of them were actually scientific in nature.

[Cliff Stamp]

That said, I'm not impressed by his addition of fuel to the pseudoscience fire.

Don't you see the issue with this statement, you have made an assertion with no justification - yet at the same time you complain about unscientific behavior where people are making conclusions which are not justified. If you find someone making a statement where their conclusion isn't justified, and you respond to this by doing the exact same thing - why would you think that would do anything productive? If you do know why a conclusion can not be justified then simply provide the justification for the refutation, simply making a claim to authority is at least as bad and possibly worse than a claim with faulty empirical justification.

If someone cites a CATRA test on a steel and then argues it shows that a steel would have high edge retention in hand and I responded to that with something like "That is a pseudoscience claim, it simply doesn't work." of what value is that statement, my criticism isn't scientific in nature either. I am simply responding to what I claim is a fallacious claim by using a logical fallacy (appeal to authority). If I want to actually make a justified argument I need to do something like cite Buck's work on the TiN blades, or Verhoeven's work, or how CATRA measurements can vary by 50% on the same piece of steel sharpened the same way, etc. .

As for the reference to ignorant people can't even tell they are ignorant. Do you really think that helps, would it be productive if someone responded to you with a paper citing the dangers of hubris? How about instead we discuss what the literature actually says vs a discussion of how great or how pitiful various people are in regards to being informed/ignorant of it.

[SpyderEdgeForever]

I have a question regarding ceramics and serrations, it ties in with what was mentioned above. I was envisioning in my mind a ceramic knife blade, similiar to an Endura, with serrations. Were you saying that unless the ceramic blade has some flex to it, the serrations would quickly snap off at the points?

[Cliff Stamp]

Were you saying that unless the ceramic blade has some flex to it, the serrations would quickly snap off at the points?

Yes, take a look at the history of ZDP-189 in serrations.

The tips of serrations are very thin, very high carbide steels don't do well in very thin sections, ceramics similar. However as noted in the above there are modern ceramics which seem to be moving past that issue. However the ceramics we see in knives are well behind current research.

[dbcad]

Deleted, only saw the first post......

[SolidState]

Well Cliff,
You seem to be missing the fact that for data to exist, a test must be done. How will I disprove nanoassembly with papers that literally cannot exist because nobody will publish them in scientific journals because scientific journals do not publish non-existent evidence? While a hilarious gambit, it is a logical farce I would expect you to understand.

Would you expect me to cite my sources as to why fairies do not exist? Would you expect me to cite my studies as to the fact that Santa is actually people's parents bringing them gifts? If not, why would you expect me to cite my sources as to why nanobot assembly lines are pseudoscience? Should I simply post a complete general chemistry textbook to the forum? Should I post an introduction to metallurgy to the forum? Do you have an idea of how to get a publisher to allow that? Also, as a PhD in the field who regularly attends conferences to share research (including the DARPA-MTO), I AM A PRIMARY SOURCE ON THIS MATERIAL - specifically on additive processing at the nanoscale. I can cite myself, and often do. Perhaps you are missing that factoid.

[Cliff Stamp]

You seem to be missing the fact that for data to exist, a test must be done.

If someone asked how come you can't simply take AEB-L and increase the hardness and just make a directly "better" knife steel, you are not in a position to wave your hands in the air like you just don't care because this experiment has not been done. You can make an argument to show there is a hard coded limit that at present we don't know how to avoid. You can explain this by siting an isothermal diagram, note what is shows would happen if you did raise the carbon content and while it would raise the hardness it would also increase the carbide fraction lowering the edge stability and it would also reduce the chromium in solution, lowering the corrosion resistance. You could then show examples of other steels and cite their material properties and how they match those kinds of predictions from the isothermals to support why you can't simply make a super-hard AEB-L, even though this obviously doesn't exist (as it can't be done), you would end up with a very different steel.

In regards to nano-bots :

"Our ability to synthesize nanometre-scale chemical species, such as nanoparticles with desired shapes and compositions, offers the exciting prospect of generating new functional materials and devices by combining them in a controlled fashion into larger structures. .....

... show that the experimental system does indeed allow the controlled fabrication of the eight different products that can be obtained with three two-state devices."

This was from an article in Nature that a friend sent me awhile back and it is easy to see that someone could read that abstract and think it is only a matter of time before we have intelligent nano-bots which are self-replicating, respond to wireless command and all kinds of extreme possibilities are well possible with star trek replicators around the corner. That is of course why abstracts use the language they do, especially if they are in Nature or similar. Now is that kind of thing possible, well anything is possible, but linking a bunch of technologies isn't trivial even when those technologies are really well known individually, trying to extrapolate where we will be and what you can get from other advancements in a generation is kind of really problematic.

If however there are actual hard coded problems which prevent various things and you want to make an argument so your audience could understand, then you note the hard coded problem and explain why to the best of the ability of what we know now why it is one and it doesn't look like it can be solved. Or you could keep making no argument, just telling people they should listen because they are ignorant and you are not - and somehow do this while criticizing them for not being scientific and not seeing the irony.

[JD Spydo]

This has been an incredibly interesting and enlightening discussion. Even though there have been a few fundamental disagreements>> but that is what makes us all think things out. I'm beginning to believe that Sintered metals and ceramics at some point are going to be a big part of Spyderco's future>> probably a super improvement in their ceramic sharpening stones if nothing else.

The information you guys have shared should be copied by anyone who is interested in this topic. I haven't seen a thread get so interesting and thought provoking since Sal Glesser had a thread about 10 years ago entitled "Let's Talk About Locks". That one used to come up from time to time and I do hope someone pulls it up again because the locking systems on folders is a huge selling point to many of Spyderco's folders.

I'm convinced that we will see sintered materials definitely play a role in the advancement of abrasives for sure. But at this point I'm not too sure about cutlery as of yet>> at least in the near future anyway. But I am convinced that we will see new abrasives that will have polishing properties as well as even, consistent abrasion.