Nanostructured steel

[Cliff Stamp]

There has been a lot of talk here about new steels and much of the discussion is around either very high carbide or some kind of exotic material - which are definitely worth considering. However I want to bring up one material, or class of material that doesn't tend to get discussed even though it is a very exciting field of research in steels which is nano-structured steel.

Steel is made out of grains, just like there are grains in wood. A fine grained steel will have an ASTM grain size of 8-9, beyond that they are considered super fine or ultra-fine or some other adjective. This means that the grains of the steel are 10 to 20 microns in size. Recently there have been developments of steels which have nano-sized grains, a nano sized grain is 1/1000 times smaller than a micron sized grain.

In some detail (who doesn't love charts) :

-grain size : https://drive.google.com/file/d/0B3dKJo ... sp=sharing" target="_blank

Now you might ask, what does it matter if the grains are micron, nano or big bad bammo in size? Well in general, glossing over a lot of physics, as grain size gets smaller good things happen. It is one of the few areas where everything increases at the same time - strength, toughness, wear resistance, sexiness, etc. .

To make this even more uber there are bainite nanostructured steels. Bainite is another form of steel which is a crystal structure like martensite but is much tougher than martensite at the same hardness. These nano-structured bainite steels have grain sizes of ~25 ASTM, this is super ultra mega fine grained steel.

Now what does all this mean, well here are some numbers of wear resistance on a few steels in a standard 3-body silica wear rest (pieces of silica are ground against the steel by a big rubber wheel, 3-body just means the slica can move around). A big number is a lower wear resistance :

1006 (mild steel) : 83
4340 at 53 HRC : 40
1060 at 63 HRC : 17
D2 at 58 HRC : 7.8

Now these numbers show some interesting effects but there is also some things about them which you really have to know about the test. Why does the mild steel only have half the wear resistance of 4340 which is much harder (mild steel can not even be HRC tested). It is because the wear resistance isn't linear and very high rates of wear will actually start to prevent further wear and there are also effects such as work hardening.

But in any case, it isn't that surprising to see the much harder 1060 surpass 4340 and then the much higher carbide volume of D2 surpass the 1060 even at a lower hardness. But here is the kicker, where does this steel fall :

1084 (nano-bainite) at 56 HRC

The answer :

1006 (mild steel) : 83
4340 at 53 HRC : 40
1060 at 63 HRC : 17
1084 (nano-bainite) at 56 HRC : 8.1
D2 at 58 HRC : 7.8

It is the same as D2 even though it is softer and has no significant carbide volume, it is referred to as carbide free and is just bainitic ferrite and austenite. In short it has similar wear resistance but it much tougher (they are not in the same class at all, this stuff is used to make armor plating).

The point of all of this is that there are ways to make steels which are much tougher, more more wear resistant and much stronger - while being just as easy to grind. It might be interesting to see what would happen if nanostructured steel was applied to edged tools.


Full paper : http://www.msm.cam.ac.uk/phase-trans/20 ... Bakshi.pdf" target="_blank

I have lots of these papers, they are pretty interesting but for now most of the research is going where the money points (shocking) so you are not likely to get cutlery specific development unless someone really is directly interested in it themselves like Verhoeven, Landes, etc. .


--

Just to clarify, the alloy content of that steel is 1084 with some light alloying to ensure bainite and prevent carbide formation and allow some retained austenite. The full details are in the paper.

[tvenuto]

My first question would be what is the cost of this material? Same order of magnitude as some of the PM steels or yet more expensive? Or are they not produced in enough quantities to warrant comparison at this point?

[Cliff Stamp]

There is nothing in the steel material, or processing which is expensive at all, I have corresponded with one of the authors of that paper before. I am going to see if I can get a piece of it after Christmas and then annoy someone enough to make a knife out of it in the early Winter.

Imagine making knives from nano-structured bainite which is tough enough to make armor plating and as wear resistant as D2. There are enough tags in that to satisfy the most weeaboo of all mall-ninjas, and its actually all true and full of science.

[tvenuto]

Not exactly a suitable material for my first home made knife project then?

[jabba359]

Nano steels? Is this really SpyderEdgeForever posting as Cliff? :p

[paladin]

Nano steels? Is this really SpyderEdgeForever posting as Cliff? :p

Hey... now, come to think about it...

they've never posted simultaneously...

it's kinda like Clark Kent & Superman-- except with nerds :p

Good catch jabba! :D

[Cliff Stamp]

Not exactly a suitable material for my first home made knife project then?

Ha, I am not sure how commercially available it is in some kind of bar stock. I have been asking around.

[SpyderEdgeForever]

Cliff, I am glad you brought this up. I have been wondering about the potential of nanostructured steel, even nanostructured carbon steel, with no exotic elements or additions.

One company called nano steel is producing some of it, supposedly cutting tools are on their sights.

http://nanosteelco.com/" target="_blank

Here is an interesting article about nano carbon in Damascus steel:

http://archaeology.about.com/od/ancient ... Blades.htm" target="_blank

[Ankerson]

Been reading about it for a few months off and on and from what I am getting out of it is that it is more for Military type of applications.

Although there has been some things mentioned about Civilian applications also like roll bars etc.

Here is one of the more basic articles on it:

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

Here is a better one:

http://www.laboratoryequipment.com/news ... rong-steel" target="_blank

[Cliff Stamp]

el is producing some of it, supposedly cutting tools are on their sights.

http://nanosteelco.com/" target="_blank

Thanks for the link, you need to be able to HIP steel to use their product at this stage though they certainly look interesting. Given the extreme results these steels are capable of they are a very exciting field of research, each time I pull up papers there are new ones.

[KevinOubre]

Cliff, how old is this technology and how do you think it would work with steels like D2 and the other carbide heavy steel? Would it not work well due to the size of the carbides form the alloying elements? Also, I am struggling to understand the wear resistance. To take your example, how can the 1084 both gain in wear resistance, up until the point that it virtually equals D2, but still retain the same eas of grinding that those steels are known for, simply from refining the grain size? Is it really possible to have our cake and eat it too? These papers are going to be some good reading when I am visiting the family.

[SolidState]

So, what you're saying is that the plate structures that are typically multiple-microns in length in bainite are somehow more powerful when not present at that scale? Forgive my ignorance, but what benefit do you get when they're smaller? I've read most of the work using TEM to observe crystalline transition at 200C, and seen the Hysitron nanoindentation data, but I don't think I was as convinced as you that you would see the benefits that you get in blades ala Howard Clark of Morgan Valley Forge.

[Cliff Stamp]

To take your example, how can the 1084 both gain in wear resistance, up until the point that it virtually equals D2, but still retain the same eas of grinding that those steels are known for, simply from refining the grain size?

I am not sure what you mean exactly, do you want the description of the wear mechanisms, they are in the paper. In any case I will give one of them. The bainite has significant retained austenite, this retained austenite when hit by an abrasive absorbs the energy of the abrasion and transforms into full hard martensite which then strongly resist abrasion. This however isn't like to happen in sharpening because you are not going to be applying the same kind of loads/speeds and thus getting the work hardening that is happening here. Now this is where another question happens - well if this was used in a knife, and the knife was used to cut normal materials would it happen there? It isn't obvious that it would. The bulk of research on these steels in regards to wear is for very harsh impact conditions hence why retained austenite tends to be so commonly used.

[Cliff Stamp]

Forgive my ignorance, but what benefit do you get when they're smaller?

Increase in strength and wear resistance and the brittle transition temperature.

I am not convinced it happens in the martensite structures we see in blades, nor even that the wear tests they do would carry over as they are often strongly dependent on the austenite transforming under abrasion to full hard martensite. The bulk of the work is on ferrite or dual phase steels, but the nano-bainite looks to have interesting properties it might make a curious machete type blade for example. In order to become even reasonably confident you would want comparisons vs common knife steels in some kind of knife-like measurement.

As an aside, there is a maker (he posts here and in most places as bluntcut), who claims to have done just that as he has made very fine grained martensite, so much so that water stops being an effective quench and he has to use an accelerated quench. He thus has UF grained martensite which he claims has very strong performance properties and he discusses this and has demonstration videos. There is metallurgy behind his claims, see for example :

"Ultrafine-grain Effect on Martensitic Transformation in a Hypereutectoid Steel - Fuliang Lian, Yongning Liu, Hongji Liu, Junjie Sun, Xuejiao Sun"

Which notes now a 1% carbon steel stops responding to water quenches when the grain size is beyond 12-13 and the very fine grain now allows diffusion based reactions (pearlite) to form significantly. The grain size has to be kept below that to avoid pearlite. Hence if you want to go beyond that you have to use a more aggressive quench (the "super quench").

What I think is an interesting question would be what are the exact material properties of say 1%C carbon with full martensite at ASTM 10 vs ASTM 15 .

Ed Fowler is another maker who champions UF grain and has lab data to show his grain sizes are very fine (much more than standard) but I doubt you would fine his experiments persuasive as they lack controls, are not even partially blinded and there is a lot of room for subjective influence.

[Bodog]

Forgive my ignorance, but what benefit do you get when they're smaller?

Increase in strength and wear resistance and the brittle transition temperature.

I am not convinced it happens in the martensite structures we see in blades, nor even that the wear tests they do would carry over as they are often strongly dependent on the austenite transforming under abrasion to full hard martensite. The bulk of the work is on ferrite or dual phase steels, but the nano-bainite looks to have interesting properties it might make a curious machete type blade for example. In order to become even reasonably confident you would want comparisons vs common knife steels in some kind of knife-like measurement.

As an aside, there is a maker (he posts here and in most places as bluntcut), who claims to have done just that as he has made very fine grained martensite, so much so that water stops being an effective quench and he has to use an accelerated quench. He thus has UF grained martensite which he claims has very strong performance properties and he discusses this and has demonstration videos. There is metallurgy behind his claims, see for example :

"Ultrafine-grain Effect on Martensitic Transformation in a Hypereutectoid Steel - Fuliang Lian, Yongning Liu, Hongji Liu, Junjie Sun, Xuejiao Sun"

Which notes now a 1% carbon steel stops responding to water quenches when the grain size is beyond 12-13 and the very fine grain now allows diffusion based reactions (pearlite) to form significantly. The grain size has to be kept below that to avoid pearlite. Hence if you want to go beyond that you have to use a more aggressive quench (the "super quench").

What I think is an interesting question would be what are the exact material properties of say 1%C carbon with full martensite at ASTM 10 vs ASTM 15 .

Ed Fowler is another maker who champions UF grain and has lab data to show his grain sizes are very fine (much more than standard) but I doubt you would fine his experiments persuasive as they lack controls, are not even partially blinded and there is a lot of room for subjective influence.

Bluntcut just had a giveaway of several unfinished knives with both a normal quench and superquench for people to experiment with. I entered and unfortunately didn't win anything. I would have beat the snot out of those blades.

[Cliff Stamp]

[...]
Bluntcut just had a giveaway of several unfinished knives with both a normal quench and superquench for people to experiment with. I entered and unfortunately didn't win anything. I would have beat the snot out of those blades.

Yeah a friend just offered to send me one, curious about the behavior. The maker is a pretty polarizing guy but he will actually defend his claims based on metallurgy and does use his knives on video and you can't ask for much more than that.

[Bodog]

[...]
Bluntcut just had a giveaway of several unfinished knives with both a normal quench and superquench for people to experiment with. I entered and unfortunately didn't win anything. I would have beat the snot out of those blades.

Yeah a friend just offered to send me one, curious about the behavior. The maker is a pretty polarizing guy but he will actually defend his claims based on metallurgy and does use his knives on video and you can't ask for much more than that.

Lucky dog. Let us know if they're all they're cracked up to be.

[Ankerson]

Forgive my ignorance, but what benefit do you get when they're smaller?

Increase in strength and wear resistance and the brittle transition temperature.

I am not convinced it happens in the martensite structures we see in blades, nor even that the wear tests they do would carry over as they are often strongly dependent on the austenite transforming under abrasion to full hard martensite. The bulk of the work is on ferrite or dual phase steels, but the nano-bainite looks to have interesting properties it might make a curious machete type blade for example. In order to become even reasonably confident you would want comparisons vs common knife steels in some kind of knife-like measurement.

As an aside, there is a maker (he posts here and in most places as bluntcut), who claims to have done just that as he has made very fine grained martensite, so much so that water stops being an effective quench and he has to use an accelerated quench. He thus has UF grained martensite which he claims has very strong performance properties and he discusses this and has demonstration videos. There is metallurgy behind his claims, see for example :

"Ultrafine-grain Effect on Martensitic Transformation in a Hypereutectoid Steel - Fuliang Lian, Yongning Liu, Hongji Liu, Junjie Sun, Xuejiao Sun"

Which notes now a 1% carbon steel stops responding to water quenches when the grain size is beyond 12-13 and the very fine grain now allows diffusion based reactions (pearlite) to form significantly. The grain size has to be kept below that to avoid pearlite. Hence if you want to go beyond that you have to use a more aggressive quench (the "super quench").

What I think is an interesting question would be what are the exact material properties of say 1%C carbon with full martensite at ASTM 10 vs ASTM 15 .

Ed Fowler is another maker who champions UF grain and has lab data to show his grain sizes are very fine (much more than standard) but I doubt you would fine his experiments persuasive as they lack controls, are not even partially blinded and there is a lot of room for subjective influence.

I am not buying into at this point other than the original uses that the steels were designed for, the Military uses etc, more impact resistant for armor plating and things like that.

As far as the wear resistance in knife blades goes I don't see how it would be of any real noticeable benefit over a similarly correctly HT blade.

Sounds more like marketing hype to me at this point, as far as knife blades go anyway, I could be wrong, but I don't believe I am, time will tell though.

Taking a terrible Heated blade and comparing it to one that is properly heat treated there is a difference in the same steel.

Bainite is basically a terrible HT as far as edge retention goes, but a great HT as far as toughness goes so I am not seeing how they believe they can get both out of a terrible HT as in more edge retention.

[tvenuto]

Are we not constantly clamoring for steels that were also not designed to be used as knife blades? Couldn't you say the exact same statement about the popular 3V/Cruwear (no wear resistance advantage/higher toughness)?

Not being contentious here, I'm actually asking if these statements are true.

[Ankerson]

Are we not constantly clamoring for steels that were also not designed to be used as knife blades? Couldn't you say the exact same statement about the popular 3V/Cruwear (no wear resistance advantage/higher toughness)?

Not being contentious here, I'm actually asking if these statements are true.

It's not about the actual steel, it more about what they are implying that they can do that I am not buying into at this point when it comes to knife blades because it just doesn't make any sense.

Take an L6 bainite Katana blade and it will do amazing things like flex into a circle and that's what it's supposed to do, but edge retention compared to an L6 blade that is HT for edge retention it would be like 2 completely different steels.

And they are if you really get right down to it, L6 bainite compared to regular L6 steel.