Ranking of Steels in Categories based on Edge Retention cutting 5/8" rope

[james terrio]

I have to disagree with your statement above about the high alloy steels not being able to handle thin low angle edges. I have worked with both 10V and O1, and performed the same tasks with both knives. Not only does the 10V knife perform all the same tasks as the O1 knife it is still extremely sharp. In carving I find that after as little as 10 minutes I can tell a considerable amount of the cutting edge of an O1 knife has gone away, but the high alloy knife is still very efficiently removing wood. The only thing you are "giving up" in the high alloy steels is ease of sharpening, but that is not really an issue for me as I use diamond stones and they do not care about alloy content. I am in no way saying that O1 is a bad steel as I cut my knife making teeth with O1 and still use it today, but given the chance I would not choose O1 over any of the higher alloy steels. This thread is not for everyone, but the benefit of it is that it compares steels of different hardness and compositions on as level a playing a field as possible.

Hear, hear :thumbup:

Toughness, even in rough use (and what some would call abuse) is not necessarily independent of, nor anathema to edge-retention. Nor is it accurate to claim that high carbide volume automatically means a blade will lack toughness. Carbide structure plays a major role for certain, but modern particle metallurgy steels address that problem very effectively.

Without hijacking the thread, my point is that nowadays you can have a high-alloy blade that will not only stand right with classic low-alloy steels in toughness, but also far out-perform them in edge-retention and corrosion-resistance - all with keen grinds and low-angle, thin edges that cut very well.

 

[chad2]

Yes but I am a huge advocate of carbon steels and it is hard to find good solid numbers for carbon steels. Also once I have set a base line for the steels used as a manufacturer heat treat I want to test custom heat treats with the same hrc. Which will give me many more categories. And the charpy test is done with much larger cross sections then most knives are made of and my test will also be measuring flexibility in the steel.

 

[james terrio]

Yes but I am a huge advocate of carbon steels and it is hard to find good solid numbers for carbon steels.

I'd love to see those kinds of numbers as well.

...my test will also be measuring flexibility in the steel.

How far and how often do you need a blade or edge to flex? Except for fairly extreme circumstances, flexibility has far more to do with geometry than steel selection or HT.

 

[Big Chris]

Yes but I am a huge advocate of carbon steels and it is hard to find good solid numbers for carbon steels. Also once I have set a base line for the steels used as a manufacturer heat treat I want to test custom heat treats with the same hrc. Which will give me many more categories. And the charpy test is done with much larger cross sections then most knives are made of and my test will also be measuring flexibility in the steel.

OK, I understand now. I did not catch it previously that you wanted to test varying heat treats. That will make a difference. Not only will different hardnesses make a difference, but also the same hardness with a different heat treat process. Vary ramp up speeds, cooling speeds and quenching speeds, thermal cycling, and varying times and temps can make differences even at the same hardness.

 

[Thomas Linton]

Would the stainless steel that has been used for "safety" razor blades for decades be "high alloy"? I think I recall that one of the Sandvik steels has been used.

I can barely recall when such blades were not stainless steel.

 

[PB Wilson]

OK, I understand now. I did not catch it previously that you wanted to test varying heat treats. That will make a difference. Not only will different hardnesses make a difference, but also the same hardness with a different heat treat process. Vary ramp up speeds, cooling speeds and quenching speeds, thermal cycling, and varying times and temps can make differences even at the same hardness.

Exactly. There's another thread in Shop Talk (if I recall correctly) where the knifemaker tested several blades but got different results from his two O1 samples because of different heat treating.

I can see this being a huge undertaking with all sorts of heat treating and tempering practices, but whenever I hear about 1095 at maximum hardness, I'm very intrigued at how it might work compared to my other 1095 blades at 58. I'd like to see where the diminishing returns levels are for 3V as well. It could go on and on, but when I saw Guy at Survive Knives stab and pry with his S90V knife I cringed and then felt really relieved that this steel that I love could handle some abuse without shattering like glass (which some thought would happen). More experiences would be of great value EVEN THOUGH the knives we might use could be apples and oranges in so many other ways.

 

[dingy]

Hear, hear :thumbup:

Toughness, even in rough use (and what some would call abuse) is not necessarily independent of, nor anathema to edge-retention. Nor is it accurate to claim that high carbide volume automatically means a blade will lack toughness. Carbide structure plays a major role for certain, but modern particle metallurgy steels address that problem very effectively.

Without hijacking the thread, my point is that nowadays you can have a high-alloy blade that will not only stand right with classic low-alloy steels in toughness, but also far out-perform them in edge-retention and corrosion-resistance - all with keen grinds and low-angle, thin edges that cut very well.

really cool man please see this (not mine knife )

http://www.cliffstamp.com/knives/forum/read.php?3,16303

 

[marthinus]

really cool man please see this (not mine knife )

Here:

http://www.bladeforums.com/forums/showthread.php/1086828-CPM-M4-at-low-angles-My-experience-recently

There are some very dramatic and somewhat misconceptions surrounding Powdered steels etc.

One should keep the following in mind when looking into Powdered and Spray metallurgy:

If we have a look in the reference: Totten, G.E. 2006. Steel Heat Treatment Metallurgy and Technologies, Second Edition. Taylor and Francis Publishers. One finds the following data on page 678. Adopted to suite this reply as I cannot get the table to work properly.

Comparison of Properties (Relative Values) of High-Speed Tool Steel Made by Various Processes Property

Ospray Metallurgy as x

Powder Metallurgy as y

Ingot Metallurgy as z

Carbide size,mm: 5–6 (x), 2–3 (y), 15–20 (z)
Bend strength: 90 (x) 100 (y) 60 (z)
Wear resistance: 100 (x) 90 (y) 100 (z)
Grindability: 80 (x) 100 (y) 25 (z)
Toughness: 90 (x) 100 (y) 60 (z)

With that said the advantages of powdered metallurgy can be summirised as:

- Finer grained and carbide distribution then ingot high alloy steels
- Easier to work with
- Better heat treat response.
- Purity of alloy

http://www.azom.com/article.aspx?ArticleID=2471

Further more one has to keep in mind the following:

1. Carbide size and it affects

http://www.smt.sandvik.com/en/produ.../knife-steel-knowledge/different-steel-types/

2. Carbide size and the affects on edge stability (work done by R. Landes).

Knife Edge Diagram

Here is what he had to say:

Dear Colleagues,

liked

http://www.schmiedecafe.com/forum/attachment.php?attachmentid=83

The following is also a good idea about Edge Stability:

http://www.smt.sandvik.com/en/products/strip-steel/strip-products/knife-steel/knife-steel-knowledge/

You will see there are pictures that show a fine micro structure steel like 12C27 compared to 440C.

you find a PDF download in english as one of my latest works, in steel & knife research ongoing in Germany.
To introduce myself I am knife maker and damascus smith since 1987 in Germany. My profession is graduated engineer in Automotive engineering and Material Science. Meber of the German Knifmakers Guild sinc 1993.

I am also author for the German Book, Messerklingen & Stahl (M&S) Technologische Betrachtung von Messerschneiden (Knife blades and Steel, A technological survey on knife edges © 2002 Wieland Verlag, Bruckmühl, Germany) witch has successfully established a high quality discussion base on scientific research towards knifes and steel. The base of the Book was developed in the early 90’s when I was in my studies.

With this download, you get a little goodie, extracted from the upcoming new book Messerklingen und Stahl, Praxishandbuch der Stähle (Knife blades and Steel; The Practical Handbook of Steels © 2005 Wieland Verlag, Bruckmühl Germany)

What is the download about?
The download shows the so-called “model of the cutting edge” taken from (M&S©2002).
The actual book will show around 50 commonly known tool steels/ -alloys used for knife applications (e.G. ATS 34, 52100, RWL 34, L6, Vascowar, M4,&#8230 an the way to treat them according to this application.

Furthermore, one will see the abilities of the steel used supporting qualities essential for knife application (e.g. edge holding, wear resistance, sharpen ability, cutting ability, cutting edge stability, corrosion resistance,&#8230, SWOT- Analysis…

The model of the edge provided here, shows 5 selected reference alloys commonly known in the worldwide knife society.
· 1.4125 (440C) Reference for traditional stainless steels
· CPM S90V Reference for modern stainless PM-steels
· Talonite Reference for Chrome Cobalt Alloys
· 1.2510 (O1) Reference for hypereutectic tool steels
· 1.2379 (D2) Reference for 12%-Chrome Cutting Steels

What Do you see?
What you see is the 1000x magnification (means all at the same scale) of the inner structure (microstructure) of this alloys, shown as micrographic pictures, in heat treated condition (Austenizing, Quench, Cryo, Temper in multiple cycles; except Talonite) Etching: Beraha 1.

The white spots, are the so-calles Carbides responsible for the wear resistance in a alloy of this kind (The Teeth), surrounded by the Matrix (Meat) (Martensit, except Talonite)

The sheet is designed to get folded on the edges marked. What you get when you do so, is the model of the edge 1000x magnification in 3D. By using the scale of the angel (Adjust in back light with single print) you can adjust every edge geometry between 15° and 90° edge angle.

This means, having the model in 3D in front of you and assuming there is a local limited load applied from a side force towards the edge (occurs constantly in the normal use of a knife), this force will deflect the edge and in dependence of the load, and the steel can take, the edge will draw back in line or chip locally (wear and loose edge).

The carbides will play a major role in the behavior of the steel in the edge
Since they are very hard and brittle, in a fine cutting edge, carbides are the first point to start with chipping, especially when the are to many in relation to the surrounding (meat) or the carbides are so large, e.g. when they will fit nicely into the full range of sharp and dull limits1)

Note, the large carbides of the alloys shown, will by no means get any significant change in size, during the complete heat treatment cycle (except 01, if hardened at to high temperatures, the carbides will dissolve completely and a mess of retained austenite and coarse brittle Martensit-grain will be there).

What you can do with it now?

Taking into account, that a sharp edge1) is around 1µm on the tip and a dull one1) is around 10µm in width, if a critical load to the edge is applied (wear of the edge), the different alloys behave different at different angles adjusted.

Print the download (use A4 for the print-format), fold at the 3 lines marked and start adjusting the angle.

I am sure this will help, to explain something…

...and hopefully start discussion …

Best regards Roman

Original thread:

http://www.bladeforums.com/forums/showthread.php/344902-Edges-and-Steels?p=3043379#post3043379

Here are also some definitions and you can see the difference between a knife steel such as 12C27 and 440C in microstructure at the edge.

http://www.smt.sandvik.com/en/products/strip-steel/strip-products/knife-steel/knife-steel-knowledge/

3. Grain size and its affects on strength

http://materion.com/~/media/Files/P...ssue No 15 - Grain Size and Material Strength
http://www.escholarship.org/uc/item/88g8n6f8

4. Alloy effects:

http://www.globalmetals.com.au/_pdf/Metallurgical_Overview/section_4.pdf
https://online.tugraz.at/tug_online/voe_main2.getvolltext?pCurrPk=32837

All of the above mentioned is dramatically affected by the heat treating process as others have stated. One can dramatically influence the structure of the steel alloy and that is why the CCT curves of an alloy is so important and to understand them as a maker when heat treating and doing research:

After these basics look into the following books (this biography is taken from hypefreeblades.com) I have not been able to obtain all of them so I cannot comment on most of them.

Metallurgy Books

Atlas of isothermal transformation diagrams
the United States Steel Company.

A compilation of transformation diagrams of many common steel alloys, with descriptions of hardenability, and various phases created by cooling from the austenitic phase.


Elements Of Hardenability
M.A. Grossman

An in-depth examination of the nature of steel hardenability which includes chapters on hardenability tests, the nature of hardening, the nature of the quenching process and the effects of alloying elements on hardenability.


Heat Treater's Guide
ASM Publication
ISBN: 0871705206

A compilation of data for each of the standard AISI grades of irons and carbon, as well as alloy, tool and stainless steels. Each data sheet gives the chemical composition of the alloy, a listing of similar U.S. and foreign alloys, its characteristics, and the recommended heat treating procedure. Most of the compilation goes much further and offers a wide variety of additional heat treating data such as representative micrographs, isothermal transformation diagrams, cooling transformation diagrams, tempering curves and data on dimensional change.


Metallurgy
Bert J. Moniz
ISBN: 0-8269-3506-0

Metallurgy covers all aspects of metallurgical engineering including the three areas of extractive, mechanical, and physical metallurgy. The textbook covers both theory and applications of metallurgical principles as applied to the conditioning, design, identification, selection, testing, and processing of metals and alloys. Topics include heat treatment, crystal structures, phase diagrams, materials standards, specific alloys, nondestructive and destructive testing, and fabrication methods. This new edition also covers the latest improvements in laboratory and industry techniques and equipment and adds new content valuable to metallurgy technicians and engineers.

Metallurgy Fundamentals
Daniel Brandt
ISBN: 0-87006-922-5

Metallurgy Fundamentals provides the student with instruction on the basic properties, characteristics, and production of the major metal families. Clear, concise language and numerous illustrations make this an easy-to-understand text for an introductory course in metallurgy. Over 450 tables, diagrams, and photographs show both the theoretical and practical aspects of metallurgy. This is perhaps the easiest to understand of any introductory metallurgy texts, Kevin Cashen says he uses this as his textbook for all of his bladesmithing metallurgy classes.

Quenching and Martempering
the ASM Committees on Quenching and Martempering

Includes chapters on methods of quenching, mechanisms of quenching, testing and evaluation of quench mediums, water and water based quench mediums, oil quenching mediums, gas quenching, factors effecting cooling rate, quenching equipment, maintenance of quenching installations, quenching of induction heated parts, quenching of flame heated parts, safety precautions, martempering methods and mediums, operation and control in martempering and equipment and handling in martempering.


Steel Metallurgy for the Non-Metallurgist
John D. Verhoeven

This book explains the metallurgy of steel and its heat treatment for non-metallurgists. It starts from simple concepts—beginning at the level of high-school chemistry classes and building to more complex concepts involved in heat treatment of most all types of steel as well as cast iron. It was inspired by the author when working with practicing bladesmiths for more than 15 years. Most chapters in the book contain a summary at the end. These summaries provide a short review of the contents of each chapter. This book is THE practical primer on steel metallurgy for those who heat, forge, or machine steel.


Tool Steel Simplified
Frank R. Palmer & George V. Luerssen

World's best selling handbook of modern practice for the man who makes tools and dies. This classic text presents detailed topics covering heat-treating methods and equipment; physical characteristics of tool steel; selecting the right tool steel for each kind of tool; properties, heat treatment, and testing of tool steel; hot acid etch test; spark testing; timbre and hardenability tests; furnace atmosphere; quenching and tempering; troubleshooting; etc. 535 pgs. Illustrated.

Contemporary Knives

An Edge in the Kitchen
Chad Ward
ISBN: 978-0-06-118848-0

An Edge in the Kitchen is the solution – an intelligent and delightful debunking of the mysteries of kitchen knives, once and for all. If you can stack blocks you can cut restaurant quality diced vegetables. If you can fold a paper airplane you can sharpen your knives better than many professionals. If you are willing to be a little adventurous you can find modern kitchen knives that outperform anything ever produced. Veteran cook Chad Ward provides an in-depth guide the most important tool in the kitchen, including choosing the best kitchen knives in your price range, practical tutorials on knife skills, a step-by-step section on sharpening, and more-all illustrated with beautiful photographs throughout. Along the way you will discover what a cow sword is, and why you might want one; why chefs are abandoning their heavy German knives in droves; and why the Claw and the Pinch, strange as they may sound, are in fact the best way to make precision vegetable cuts with speed and style. An Edge in the Kitchen is the one-and-only guide to the most important tool in the kitchen.

Messerklingen und Stahl
Roman Landes
ISBN: 978-3-938711-04-0

A ground breaking work in modern applications of steel for knife edges supported by almost a century of studies on that specific topic. Thus far it is only in German.

 

[marthinus]

IMO all steels have pros and cons. The user has to decide what he wants more in his tools between the different properties or characteristics he/she wants:

Lets look at characteristics of steel:

Edge performance
Edge performance consists of three elements: sharpness, edge stability and wear resistance.

Sharpness
The ability of the steel to support a keen edge with razor sharpness. It also means that the knife will be easy to resharpen. This is important for all knives.

Edge stability
The ability for the knife edge to withstand edge rolling and edge micro-chipping. Rolled edges and micro-chipped edges are the most common reasons for resharpening. This is important for all knives.

Wear resistance
The ability for the edge to resist abrasive wear. This is usually secondary to edge stability issues, such as micro-chipping or edge rolling.

Toughness
Toughness is the resistance of the knife to cracking. Cracks always start at a weak point in the steel, such as an inclusion or a large primary carbide. So toughness is enhanced by a homogeneous structure that is free from impurities and large carbides. A fine-carbide steel grade will always have higher toughness than a coarse-carbide grade with a given hardness. Toughness is vital for professional and military knives.

Corrosion resistance
Corrosion resistance should be selected to suit the application. Since high corrosion resistance involves sacrifices in edge performance, the best approach is to have corrosion resistance that is 'good enough' for the selected type of knife. An everyday carry knife and a fishing knife will make very different demands on corrosion resistance.

Strength
: The ability to take a load without permanently deforming. For many types of jobs, strength is extremely important. Any time something hard is being cut, or there's lateral stress put on the edge, strength becomes a critical factor. In steels, strength is directly correlated with hardness -- the harder the steel, the stronger it is. Note that with the Rockwell test used to measure hardness in a steel, it is the hardness of the steel matrix being measured, not the carbides. This, it's possible for a softer, weaker steel (measuring low on the Rockwell scale) to have more wear resistance than a harder steel. S60V, even at 56 Rc, still has more and harder carbides than ATS-34 at 60 Rc, and thus the S60V is more wear resistant, while the ATS-34 would be stronger.

Source: Sandvik knife steel knowledge and Zknives: Knife Steel FAQ

Ok....I just lost my trend of thought and am confusing myself now. Hope this helps for some.

 

[dingy]

tons of thanks for you info, cool. marthinus

 

[chiral.grolim]

IMO all steels have pros and cons. The user has to decide what he wants more in his tools between the different properties or characteristics he/she wants:

Lets look at characteristics of steel:

Edge performance
Edge performance consists of three elements: sharpness, edge stability and wear resistance.

Sharpness
The ability of the steel to support a keen edge with razor sharpness. It also means that the knife will be easy to resharpen. This is important for all knives.

Edge stability
The ability for the knife edge to withstand edge rolling and edge micro-chipping. Rolled edges and micro-chipped edges are the most common reasons for resharpening. This is important for all knives.

Wear resistance
The ability for the edge to resist abrasive wear. This is usually secondary to edge stability issues, such as micro-chipping or edge rolling.

Toughness
Toughness is the resistance of the knife to cracking. Cracks always start at a weak point in the steel, such as an inclusion or a large primary carbide. So toughness is enhanced by a homogeneous structure that is free from impurities and large carbides. A fine-carbide steel grade will always have higher toughness than a coarse-carbide grade with a given hardness. Toughness is vital for professional and military knives.

Corrosion resistance
Corrosion resistance should be selected to suit the application. Since high corrosion resistance involves sacrifices in edge performance, the best approach is to have corrosion resistance that is 'good enough' for the selected type of knife. An everyday carry knife and a fishing knife will make very different demands on corrosion resistance.

Strength
: The ability to take a load without permanently deforming. For many types of jobs, strength is extremely important. Any time something hard is being cut, or there's lateral stress put on the edge, strength becomes a critical factor. In steels, strength is directly correlated with hardness -- the harder the steel, the stronger it is. Note that with the Rockwell test used to measure hardness in a steel, it is the hardness of the steel matrix being measured, not the carbides. This, it's possible for a softer, weaker steel (measuring low on the Rockwell scale) to have more wear resistance than a harder steel. S60V, even at 56 Rc, still has more and harder carbides than ATS-34 at 60 Rc, and thus the S60V is more wear resistant, while the ATS-34 would be stronger.

Source: Sandvik knife steel knowledge and Zknives: Knife Steel FAQ

Ok....I just lost my trend of thought and am confusing myself now. Hope this helps for some.

^THIS is the portion I take issue with here, and with Landes' definition of "sharp" and "dull". By his definition, a knife which cannot cut 'cleanly' through phonebook paper (or media of similar thinness and stiffness) is "dull" even if it can cut 'cleanly' through printer paper, cardboard, carve wood, slice a tomato, etc. His "sharp" is ophthalmologist sharp - for use on sensitive conjuctiva. It is ONLY achievable for any length of time with the VERY fine grains of <1 micron, and the edge-stability can only be measured in cutting very fine materials. Put that fine edge to a piece of cardboard and it is gone in a matter of inches due to the abrasive nature of the substrate. Then you are left with a knife which Landes considers "dull" but may be perfectly suited to the task at hand, except that the low (and softer) carbide volume means it won't last long compared to the high-carbide PM steel. The edges that Landes is talking about are irrelevant to most cutting applications for this reason. You don't need an edge that sharp for most cutting applications, you need an edge that will last at a particular level of sharpness, a level that he calls "dull". Why is the "dull" edge sufficient? Because while the apex starts the cut, the bevel faces carry it through, forcing the material apart and enduring much abrasion and bending and impact stress. The force required to push the widening bevel through the material is VASTLY greater than the force at the apex. If the material being cut is much thicker (i.e. requires a much deeper cut) than the difference in edge-bevel height between a fine-grained edge-stable steel blade and a less fine-grained less edge-stable PM steel blade, the user won't notice any advantage to the finer edge, especially when it "dulls" to the point of failing to complete the cut through the thicker or more abrasive material so much faster than the high-wear PM steel.

That is my challenge here. What is "dull"? An apex diameter of only 10um? What can a 10um apex not cut through with relative ease? Doesn't it depend more on the thickness of material behind that apex?

 

[Big Chris]

I think that this is why the testing that Jim is doing here is so invaluable. With his method of measuring the amount of force applied to the cut all knives are basically at the same level of "dullness" when the testing is complete. I know there is still the human factor, but his methods are repeatable within plus or minus 10 cuts. When he has steels that will make 800 cuts that becomes a very small percentage.

 

[chiral.grolim]

Jim is sharpening to 6000 Grit on an Edge Pro = 1 micron scratch pattern. That is more than a "fine" finish for a utility knife, not the level of refinement you'd expect from the average Joe. If we assume that Jim knows how to sharpen all the way to the apex and eliminate a wire/foil-edge, what apex diameter would you guess (since we don't have an SEM for confirmation) he has achieved on each knife prior to testing? Here are SEMs of a razor-blade sharpened on a Shapton 8000 grit hone which is 1.84 micron to achieve 0.2 um apex diameter:

http://straightrazorplace.com/advanced-honing-topics/99196-0-25-micron-diamond-spray-sem.html

If Jim is achieving a similar apex thickness on each knife BEFORE testing, and each seems to require ~15 lbs, how thick do you think the apex has become when it reaches 20 lbs? What percent-loss of sharpness is that 5-lb increase?

Even at such a high level of edge-refinement where the <1 micron carbide steels would perhaps excel by retaining sharpness much longer, they do not. But this is slicing cuts, and such high edge-refinement is not advantageous. Jim shows that in a coarse finish slicing rope, those fine carbides and 1 micron (Landes' "sharp") edge are even less important than carbide volume and hardness provided that a 'relatively' thin edge is maintained. Would <1 micron carbides improve the wear-resistance of steels like K390? I'd expect so, so long as carbide volume is maintained.

Landes is too focused on apex geometry and seems to miss edge geometry. But I'd love to be shown my error in that.

 

[marthinus]

^THIS is the portion I take issue with here,

Why do you have an issue with this?

From my understanding one requires an alloy with edge stability properties, heat treated correctly of coarse, in order for those wear resistant carbides to have any benefit at all. IMO without edge stability properties wear resistance would be worthless, regardless of edge angle. I believe grain size comes into play here as well. Not only carbide size.

That is my challenge here. What is "dull"?

Hard to put an accurate value on that. R. Landes has some extreme views on sharpness no doubt. His dull might still be my extremely sharp. However, he remains a qualified metallurgist and I only have an opinion drawn from his work. There really is limited amount of published research such as his on knives specifically.

An apex diameter of only 10um? What can a 10um apex not cut through with relative ease?

Shaving like a straight razor comes to mind. If we look at the experiments done on sharpening by J.D Verhoeven we can see edges of 0.35-1 micron. 10 Micron seems significantly larger...

Experiments on Knife Sharpening. John D. Verhoeven

Doesn't it depend more on the thickness of material behind that apex?

Behind the apex....ie the geometry?

IMO this is a major roll in performance. This is why we see such great work by Phil Wilson to name but one. Ground thin, good heat treat, small apex edge.....what is not to like and most people would agree Phil Wilson has some fine edges on a knife. Jim mentioned:

The Custom Phil Wilson knives in M390 (62) and ELMAX (62) are not added to the data, they wouldn't fit into any of the Categories due to the Optimal HT and cutting ability, the difference is off the scale percentage wise so it wasn't added.

It would be interesting if one could get one of R.Landes knives....might also be off the scale percentage wise even though they are using lower alloy steels but he applies optimal heat treat and cutting ability.

......
More important is the shape of the blade. For any cutting action all blades shall be designed to be as slim as possible to get maximum performance. Many makers just focusing on fancy style, hype material or wicked HT, to pretend they made a high performance blade. But when it comes down to cutting performance its geometry that overrules them all.
And just by looking at a blade and its geometrical figures you can tell right away if the combination of steel, HT and geometry make any sense at all.

To give you an example of this:
Employing D2 on a chopper (6mm strong blade) or even use it for a straight razor, are just 2 examples for a fully blown "genuine error".
Why? Cutting task and required geometry, simply don't fit the the alloys properties at all.

This now brings me to the important question of how do geometry, steel and HT work together?

The goal for making a usable knife is to get as much performance out of it to show superiority over the mainstream.

First and most important property is that this thing cuts like hell. Means "cutting ability" is the thing to focus on, mans slim and fine geometry. (geometry cuts)
Second this edge should last long. This is where the material properties come in (Alloy and HT). (The harder the better in relation to toughness)
Fine edges can hold their edge better when HT and alloy are chosen right. and the better HT and material properties are the slimmer the blade can be made and the more acute the angel of the edge can be made. Using this potential offered by right HT and alloy you than can make the edge even slimmer and sharper than before adding more cutting ability to it. This circle of optimizing can be done as fas as user behavior or initial cutting task limit it.

I have one question thought. Why do you mean by

edge-stability can only be measured in cutting very fine materials

?


If we go by the definition of edge Edge stability "The ability for the knife edge to withstand edge rolling and edge micro-chipping. Rolled edges and micro-chipped edges are the most common reasons for resharpening. This is important for all knives." One should expect this to be true even if the steel is used on hard, thick materials.

Here is a nice test by Gavko showing how much punishment a thin grind, well heat treated steel can take that is considered a "low" wear resistant steel but with higher edge stability.

[video=youtube;krZJUj70r1c]http://www.youtube.com/watch?v=krZJUj70r1c[/video]

IMO there is no be all end all of steels. We are spoiled for choice and one can pick your poison so to speak.

 

[chiral.grolim]

Thank you for replying.

Why do you have an issue with this?

From my understanding one requires an alloy with edge stability properties, heat treated correctly of coarse, in order for those wear resistant carbides to have any benefit at all. IMO without edge stability properties wear resistance would be worthless, regardless of edge angle. I believe grain size comes into play here as well. Not only carbide size.

My issue is that you separated "wear resistance" and also "toughness" from "edge stability" and declared it "secondary", and here you toss out edge angle too. But wear resistance, like toughness, is a primary attribute, a determinant in choosing the correct steel for a given application. AEB-L or 13C26 may be significantly more edge-stable than CPM110V, for example, as the grains are much finer. Based on grain size, they can be taken to a much thinner edge-width to increase cutting performance provided that the strength afforded by the finer grains is not exceeded by a given application. However, the wear resistance is so much lower than CPM110V that, for a given application, the finer-grained steel would have to be taken out of operation and resharpened more often due to rapidly increasing edge width, increasing faster than the relatively "unstable" CPM110V. And what happens if the application exceeds the strength of that finer edge? You lose it, and with it the primary advantage offered by the steel.
Now, to mitigate the issue of edge strength in regards to stability, you might increase the geometry slightly (as Verhoeven's paper recommends), but how much thinner is this newer, more stable geometry than that at which the CPM110V blade is stable? Is the added thinness even noticeable to the user in terms of cutting efficiency? If not, the difference in edge stability becomes not only secondary but irrelevant when comparing these steels. Toughness and wear-resistance are paramount.

In summation, I take issue with making a primary practical concern "secondary" to a material property that may be irrelevant to the application, or even to most applications.

Hard to put an accurate value on that. R. Landes has some extreme views on sharpness no doubt. His dull might still be my extremely sharp. However, he remains a qualified metallurgist and I only have an opinion drawn from his work. There really is limited amount of published research such as his on knives specifically.

It is difficult because it misses the point (pun intended). "Dull" is determined by the application, i.e. "when it won't cut what I need it to cut as easily as I need it to cut it." This MUST be the case or even Landes' "sharp" falls short. It is one of my favorite points of knife geometry that the "tangent" to an apex is perpendicular to the cutting edge, i.e. every knife which has ANY apex thickness is "dull" from some point of reference. But to a user who needs an edge that cuts a particular medium very well for a very long time, 10 micron might be perfect. Would he prefer <1 micron? Absolutely IFF it lasts as long as he needs it to.

Shaving like a straight razor comes to mind. If we look at the experiments done on sharpening by J.D Verhoeven we can see edges of 0.35-1 micron. 10 Micron seems significantly larger...

Experiments on Knife Sharpening. John D. Verhoeven

Yup, read it. 10 micron certainly does seem large. But shaving my face, like ophthalmic surgery, doesn't entail a great deal of abrasion or impact or lateral stress, doesn't require a great deal of force, AND does not require an extremely low edge angle if thinness is maintained a bit back from the apex. I can shave my face with a 45-dps (90 inclusive) blade if the apex is that fine and shoulder thickness is low (e.g. 1 mm, not really all that thin). This is a VERY robust edge, quite stable even for large-grained steels. The key is that the material being cut isn't very thick and will readily separate upon cleavage. I just need a very fine edge to make that cleavage as clean as possible to avoid tugging and stress the surrounding material.

But that is shaving and surgery. Carving wood or cutting up rope and cardboard, how fine does my edge need to be? The material being cut is stiff and strong, and rope & cardboard are abrasive. If completion of the cut requires more force than shaving or surgery, and if that force or the abrasion destroys a fine edge so quickly it offers almost no noticeable advantage, then it is irrelevant.

Behind the apex....ie the geometry?

IMO this is a major roll in performance. This is why we see such great work by Phil Wilson to name but one. Ground thin, good heat treat, small apex edge...
...
It would be interesting if one could get one of R.Landes knives....might also be off the scale percentage wise even though they are using lower alloy steels but he applies optimal heat treat and cutting ability.

Specifically the geometry behind the apex, i.e. the increasing thickness of the bevels which, on a deep cut (i.e. NOT shaving or surgery or slicing newsprint and pages of telephone books) must help force apart the material. Gavkoo's video demonstrates well how important, indeed how much more important that geometry is compared to the apex refinement - how important was the edge refinement to cutting through kydex and wire and sheet-metal?

My point, judging the steel based on how fine the apex can be made is silly if the stress to which the blade is subjected annihilates it in the steel with higher edge stability, or if the geometry going back to the spine of the knife isn't optimized for the application. Phil Wilson uses some "brittle" steels with supposedly low edge-stability compared to Sanvik's razor-blade steel - Would Landes criticize him for this?

Jim has tested fine-grained 13C26 and Aus8A and they landed in his "Category 7" - that's a FAR cry from Category 1, but perhaps a different the heat treatment could close the gap? I am skeptical, but would like to see it.

I have one question thought. Why do you mean by ?

edge-stability can only be measured in cutting very fine materials

If we go by the definition of edge Edge stability "The ability for the knife edge to withstand edge rolling and edge micro-chipping. Rolled edges and micro-chipped edges are the most common reasons for resharpening. This is important for all knives." One should expect this to be true even if the steel is used on hard, thick materials...

No.
If you compare the edge stability of a steel with <1 micron grains to one with ~10 micron grains both sharpened to 15-dps, the detectable difference is lost if the cutting includes forces that exceed the strength of either steel below a given thickness. For example, Crucible touts S90V's higher toughness (via Charpy C-notch) than 440C, but the listed difference is only 4 J/cm2. Could you tell the difference in weight between lifting a sack of 22 apples vs 26 apples? THAT is the difference, i.e. negligible - in use, 440C and S90V are equivalently tough, but only at THAT geometry. Thicker geometry might show NO difference, while MUCH thinner geometry might show a great deal more difference but only if the level of precision of detection is there to catch it, and only if the stress inflicted is low enough to accentuate the difference. Smack both into a brick with a very thin, very fine edge, you might not notice a difference even under SEM because the stress was too high. Repeat the same test with a very thick edge and you STILL probably wouldn't see a difference because the geometry was too thick.

If the fine grained steel can only demonstrate the enhanced edge-stability in limited circumstances, i.e. cutting very fine materials (shaving, surgery), then that feature is only an advantage under those limited circumstances. Cutting harder/thicker materials might require a stronger edge (thicker geometry) where grain-size becomes less important, and may NOT require a very fine edge (where that stability shows itself).

I'm starting to babble now so will stop here.

 

[chiral.grolim]

double-tap

 

[jdm61]

I echanged PM's/Emails with Roman Landes a few years back. The one thing that I got out of talking with him was that with the steeels that I was using, mostly W2, Cru Forge and 1084 at the time, he basically said that there was no earthly reason to have ANY knife leave my shop any softer than 60Rc if I was doing the HT right, None has left my shop any softer than that to the best of my knowledge and I have had zero complaints.

 

[marthinus]

Thank you for replying.
My issue is that you separated "wear resistance" and also "toughness" from "edge stability" and declared it "secondary", and here you toss out edge angle too.

I did not. The resource: Sandvik knife steel knowledge does.

But wear resistance, like toughness, is a primary attribute, a determinant in choosing the correct steel for a given application. AEB-L or 13C26 may be significantly more edge-stable than CPM110V, for example, as the grains are much finer.

In summation, I take issue with making a primary practical concern "secondary" to a material property that may be irrelevant to the application, or even to most applications.

Let us have a look at where you have this issue:

Edge stability
The ability for the knife edge to withstand edge rolling and edge micro-chipping. Rolled edges and micro-chipped edges are the most common reasons for resharpening. This is important for all knives.

Wear resistance
The ability for the edge to resist abrasive wear. This is usually secondary to edge stability issues, such as micro-chipping or edge rolling.

My interpretation is as follows. Without edge stability (to withstand edge rolling and edge micro-chipping) wear resistance would mean squat as the wear resistant carbides would just chip out. A steel alloy needs a certain amount of edge stability to even be able to support wear resistance.

Based on grain size, they can be taken to a much thinner edge-width to increase cutting performance provided that the strength afforded by the finer grains is not exceeded by a given application.

Strength is also applicable to high wear resistant steels. As mentioned Strength is:

The ability to take a load without permanently deforming. For many types of jobs, strength is extremely important. Any time something hard is being cut, or there's lateral stress put on the edge, strength becomes a critical factor. In steels, strength is directly correlated with hardness -- the harder the steel, the stronger it is. Note that with the Rockwell test used to measure hardness in a steel, it is the hardness of the steel matrix being measured, not the carbides. This, it's possible for a softer, weaker steel (measuring low on the Rockwell scale) to have more wear resistance than a harder steel. S60V, even at 56 Rc, still has more and harder carbides than ATS-34 at 60 Rc, and thus the S60V is more wear resistant, while the ATS-34 would be stronger.

Other referenced material I posted:

3. Grain size and its affects on strength

http://materion.com/~/media/Files/PD...ial Strength
http://www.escholarship.org/uc/item/88g8n6f8

IMO it stands to reason, the larger the carbide size and grain size of a steel the lower the strength. Powdered metallurgy has improved strength over its similar ingot steel. No doubt about that. However, I am still waiting for a high alloy steel such as used in the plastic mold industry to pass a Bladesmith bend test.....

However, the wear resistance is so much lower than CPM110V that, for a given application, the finer-grained steel would have to be taken out of operation and resharpened more often due to rapidly increasing edge width, increasing faster than the relatively "unstable" CPM110V.

I agree. Especially if you use your knife to lower sharpness (not shaving). This is where high carbide steels come into their own in cleaner materials. In my experience, no matter the steel a day on the farm and it is dull. Sharpening to low angles (something I learned from my grandfather) I have chipped my CPM-M4 badly. As you can see from the picture above. My lower alloy steels that are higher in edge stability and lower in wear resistance had only rolled their edges, and at 5 dps is a breeze to touch up. And I do not have to sharpen out chips.

If CPM-110V chips out with one cut such as the CPM-M4 blade did would it not also be taken out of use after one cut and be sharpened? Would the higher edge stability blade with similar edge angle not continue to out perform the micro chipped blade despite it has experienced rolling?

Of course one can offset this lower edge stability by applying a micro-macro bevel on the higher wear resistant steel case in point, the CPM-M4 Gayle Bradley again.

And what happens if the application exceeds the strength of that finer edge? You lose it, and with it the primary advantage offered by the steel.

Yes, it will role. What about higher wear resistant steels? They will micro-chip or chip out if all you chased in performance was wear resistance. What would you prefer happen between edge rolling and chipping?

Now, to mitigate the issue of edge strength in regards to stability, you might increase the geometry slightly (as Verhoeven's paper recommends), but how much thinner is this newer, more stable geometry than that at which the CPM110V blade is stable?

If an 1075/1055 blade for example is heat treated properly you should not have an issue with "edge strength" and no increase in geometry is necessary. Heck, that is why they are called High Strength Low Alloy steels. Ones geometry can actually be significant thinner then that of a CPM110V blade without sacrificing strength.

Is the added thinness even noticeable to the user in terms of cutting efficiency?

For the average user...good point, don't know. For me personally, yes.

If not, the difference in edge stability becomes not only secondary but irrelevant when comparing these steels. Toughness and wear-resistance are paramount.

Toughness
Toughness is the resistance of the knife to cracking. Cracks always start at a weak point in the steel, such as an inclusion or a large primary carbide. So toughness is enhanced by a homogeneous structure that is free from impurities and large carbides. A fine-carbide steel grade will always have higher toughness than a coarse-carbide grade with a given hardness. Toughness is vital for professional and military knives.

Lets look at Zknives.com

:Toughness
The ability to take an impact without damage, by which we mean, chipping, cracking, etc. Toughness is obviously important in jobs such as chopping, but it's also important any time the blade hits harder impurities in a material being cut (e.g., cardboard, which often has embedded impurities).

The knifemaker will be making a tradeoff of strength versus toughness. Generally speaking, within the hardness range that the steel performs well at, as hardness increases, strength also increases, but toughness decreases. This is not always strictly true, but as a rule of thumb is generally accurate. In addition, it is possible for different heat treat formulas to leave the steel at the same hardness, but with properties such as toughness, wear resistance, and stain resistance significantly differing.

"Finer grain size improves toughness" :Arthur C. Reardon, 2011. Metallurgy for the Non-Metallurgist, Second Edition. ASM International.

It seems toughness is more in favor of the lower alloy steel that offers greater edge stability.

It is difficult because it misses the point (pun intended). "Dull" is determined by the application, i.e. "when it won't cut what I need it to cut as easily as I need it to cut it." This MUST be the case or even Landes' "sharp" falls short. It is one of my favorite points of knife geometry that the "tangent" to an apex is perpendicular to the cutting edge, i.e. every knife which has ANY apex thickness is "dull" from some point of reference. But to a user who needs an edge that cuts a particular medium very well for a very long time, 10 micron might be perfect. Would he prefer <1 micron? Absolutely IFF it lasts as long as he needs it to.

I have absolutely no idea what you mean by the bold bit.

My point, judging the steel based on how fine the apex can be made is silly if the stress to which the blade is subjected annihilates it in the steel with higher edge stability,

In what form was the AEB-L blade of Gavko "annihilated". Do you feel a similar ground blade in CPM-110V would fair the same or even better?

Phil Wilson uses some "brittle" steels with supposedly low edge-stability compared to Sanvik's razor-blade steel - Would Landes criticize him for this?

It is not my place to say what R. Landes would do or not. I respect both for their knife applications.

Jim has tested fine-grained 13C26 and Aus8A and they landed in his "Category 7" - that's a FAR cry from Category 1, but perhaps a different the heat treatment could close the gap? I am skeptical, but would like to see it.

I believe it would be similar to this:

"The Custom Phil Wilson knives in M390 (62) and ELMAX (62) are not added to the data, they wouldn't fit into any of the Categories due to the Optimal HT and cutting ability, the difference is off the scale percentage wise so it wasn't added."

If it is ground properly and is heat treated optimally. If that is the case would it out perform many of the listed steel?

Where would you say a knife like this would end up? Photo by cKc Knives.

If you compare the edge stability of a steel with <1 micron grains to one with ~10 micron grains both sharpened to 15-dps, the detectable difference is lost if the cutting includes forces that exceed the strength of either steel below a given thickness.

With all due respect. 15 dps is IMO appropriate for a axe and heavy use. Heck, most of the higher wear resistant steels I have used (CPM-M4, M390, S30V) all are stable at 10-12 dps.

If the fine grained steel can only demonstrate the enhanced edge-stability in limited circumstances, i.e. cutting very fine materials (shaving, surgery), then that feature is only an advantage under those limited circumstances. Cutting harder/thicker materials might require a stronger edge (thicker geometry) where grain-size becomes less important, and may NOT require a very fine edge (where that stability shows itself).

But fine grained steel is not limited to fine materials. Fine grained steels show their worth in larger blades splitting bone, chopping trees, etc. Dan Keffeler shows this well with his use of CPM-3V blades ground thin in their geometry.

[video=youtube;6wQ7fo9x0ac]http://www.youtube.com/watch?v=6wQ7fo9x0ac[/video]

cKc knives again testing AEB-L, thinly ground.

[video=youtube;akTNcbpm9yw]http://www.youtube.com/watch?v=akTNcbpm9yw[/video]

I remain of the opinion there are steels to suite all needs. People can decide for themselves what they like but the big difference comes in when someone knows what they are doing with regards to grinding the geometry and heat treat. I would rather take a 1055 blade heat treated and ground well then a CPM-110V, K390, Unobtainium super alloy that glows when you cut that is heat treated like a donkeys rear.

 

[sodak]

Here is a nice test by Gavko showing how much punishment a thin grind, well heat treated steel can take that is considered a "low" wear resistant steel but with higher edge stability.

[video=youtube;krZJUj70r1c]http://www.youtube.com/watch?v=krZJUj70r1c[/video]

IMO there is no be all end all of steels. We are spoiled for choice and one can pick your poison so to speak.

I didn't hear him mention what steel/hardness that was. Interesting video!

 

[chiral.grolim]

...

My interpretation is as follows. Without edge stability (to withstand edge rolling and edge micro-chipping) wear resistance would mean squat as the wear resistant carbides would just chip out. A steel alloy needs a certain amount of edge stability to even be able to support wear resistance.

There are no published values of steel "edge stability". Instead, there are published values of toughness and comparative wear resistance at given geometries. Obviously these two properties depend on stability of the steel matrix, but they are not "secondary" to it, for they are the practical properties sought after - i.e. "primary". The instability of the edge with larger carbides, i.e. the tendency of those carbides to chip-out, depends upon two key factors - thickness of that edge (how much material surrounds/supports the carbides) and how much support that material actually offers (how well it retains the carbides against stress).

The user requires an edge that resists abrasion - this is achieved by more and harder carbides. Ferric carbides cannot compete with vanadium carbides for abrasion resistance, nor can chromium carbides. To fail by abrasion, the carbides must be cut or cracked/torn out of the matrix as it abrades away. This happens more easily with the ferric carbides and chromium carbides as demonstrated by edge-retention tests, which essentially measure how quickly edge thickness increases. Again, this compares steels like S90V to Aus8A and 13C26 - 10 micron vs 1 micron carbides. If "edge stability" were primary, we know that 13C26 would resist abrasion longer than S90V... but it does not except for a very brief period/distance of cutting which is irrelevant to most tasks involving abrasion. Thus "edge stability" is secondary. At an overly thin geometry and sufficient application of stress, the larger carbides would indeed chip-out... UNTIL there is sufficient material support from the matrix to hold onto the carbides while the carbides protect the matrix from the abrasive wear, i.e. an edge-stable geometry. The larger carbide S90V reaches this edge-stable geometry a little more quickly than the smaller carbide 13C26, but holds a thinner edge for much longer, and that edge-stable geometry is thin enough for the application. Does that mean S90V has greater "edge stability" than 13C26, despite larger carbides?

The user requires an edge that resists cracking - this is achieved with finer carbides or more austenite, yes? A softer steel with larger carbides may resist cracking better than a harder steel with finer carbides, not so? And since abrasion resistance depends NOT on matrix hardness so much as carbide hardness and content, a softer steel with larger carbides can be both tougher (resist cracking) AND more abrasion resistant than the harder steel with finer carbides.

The user requires an edge that resists compression/deformation - this is achieved with harder (stronger) matrix:

... Strength is... The ability to take a load without permanently deforming. For many types of jobs, strength is extremely important. Any time something hard is being cut, or there's lateral stress put on the edge, strength becomes a critical factor. In steels, strength is directly correlated with hardness -- the harder the steel, the stronger it is. Note that with the Rockwell test used to measure hardness in a steel, it is the hardness of the steel matrix being measured, not the carbides. This, it's possible for a softer, weaker steel (measuring low on the Rockwell scale) to have more wear resistance than a harder steel. S60V, even at 56 Rc, still has more and harder carbides than ATS-34 at 60 Rc, and thus the S60V is more wear resistant, while the ATS-34 would be stronger.

...

IMO it stands to reason, the larger the carbide size and grain size of a steel the lower the strength. Powdered metallurgy has improved strength over its similar ingot steel. No doubt about that. However, I am still waiting for a high alloy steel such as used in the plastic mold industry to pass a Bladesmith bend test.....

:thumbup: Yes, larger carbides should lower strength IF the geometry is thin enough and the force application careful enough to demonstrate it. How thin?? As you quoted above, it is the matrix that gives strength, not the carbides. What is the proportion of carbide to matrix and how thin of a geometry is required before a substantial reduction in strength is noted?? What is the UTS of S90V vs that of 13C26 when both are at 60 Rc? Discernible? At what geometry is it discernible?

... In my experience, no matter the steel a day on the farm and it is dull. Sharpening to low angles (something I learned from my grandfather) I have chipped my CPM-M4 badly. As you can see from the picture above. My lower alloy steels that are higher in edge stability and lower in wear resistance had only rolled their edges, and at 5 dps is a breeze to touch up. And I do not have to sharpen out chips.

If CPM-110V chips out with one cut such as the CPM-M4 blade did would it not also be taken out of use after one cut and be sharpened? Would the higher edge stability blade with similar edge angle not continue to out perform the micro chipped blade despite it has experienced rolling?

Of course one can offset this lower edge stability by applying a micro-macro bevel on the higher wear resistant steel case in point, the CPM-M4 Gayle Bradley again.

And here is my question - WHY use a high-wear steel for applications where high wear-resistance isn't relevant? I am continually confused by criticism of high-wear steels vs finer carbide steels in applications that are not abrasive.
And also, why is such a low angle required/desired? Is an apex bevel so difficult to establish or so debilitating to performance? Furthermore, out of curiosity did you grind away the weak or "burnt" CPM-M4 from the Spyderco prior to testing? Is it possible that the steel behind the edge wouldn't behave the same if so tested again? Have you repeated the test on the same knife with the edge-metal removed?

It sounds like the steels featured equal strength - both suffered edge-damage from the stress encountered - but i wonder if the damage wasn't due to strength but "toughness", namely impact against sand or impurities, in which case the tougher steel deforms rather than cracks. If the CPM-M4 chipped out from simple carving of hardwood where the other steel bent out of alignment, it was clearly a "strength" issue. You seem to prefer restoring a bent edge which will eventually fracture away to a slight increase in edge thickness which could lend a substantial increase in wear resistance with little loss of cutting efficiency in the CPM-M4 blade... but if wear resistance isn't beneficial to you, why bother with the steel at all?

Yes, it will role. What about higher wear resistant steels? They will micro-chip or chip out if all you chased in performance was wear resistance. What would you prefer happen between edge rolling and chipping?

You are assuming that the application will only bend the edge, and only to within its ability to resist fracture - why? Do you think that these finer grain steels won't chip? INFI !!! But rolled edges also fracture. I would prefer an edge that remains thinner longer - a rolled edge can easily be thicker than a chipped edge. If the chipped edge is thinner and continues cutting at the performance level i need for longer ...

If an 1075/1055 blade for example is heat treated properly you should not have an issue with "edge strength" and no increase in geometry is necessary ... can actually be significant thinner then that of a CPM110V blade without sacrificing strength.

Again, ONLY IF the matrix provides sufficient support for the application. HOW MUCH thinner can the edge be than the S110V edge and still be strong enough for the application, and HOW MUCH thicker must be the S110V edge that the loss in cutting performance is really noticeable? Is it like the toughness comparison of 22 J vs 26 J? One is technically tougher, but both can handle 20 J and neither can handle 30 J, and the difference between them isn't enough to notice in most applications. I worry that that is the case here but regarding strength rather than toughness. I'd like to be shown otherwise.

For the average user...good point, don't know. For me personally, yes.

THE POINT.

Toughness is the resistance of the knife to cracking. Cracks always start at a weak point in the steel, such as an inclusion or a large primary carbide. So toughness is enhanced by a homogeneous structure that is free from impurities and large carbides. A fine-carbide steel grade will always have higher toughness than a coarse-carbide grade with a given hardness...
...
It seems toughness is more in favor of the lower alloy steel that offers greater edge stability.

Do you have any Charpy or other standardized impact toughness values for these fine grained steels like 13C26 or AEB-L or Aus-8A? Because 52100 and O1 (fine-grain tool steels) are supposedly lower than that of CPM-M4 (not so fine-grained and much higher carbide volume) but all measure around 40 J/cm2. Stainless steels usually measure lower. I would LOVE to see the 13C26 data. My point - I am not seeing the detriment of these 10 micron carbides in the data beyond very fine edges for surgery & shaving.

It is difficult because it misses the point (pun intended). "Dull" is determined by the application, i.e. "when it won't cut what I need it to cut as easily as I need it to cut it." This MUST be the case or even Landes' "sharp" falls short. It is one of my favorite points of knife geometry that the "tangent" to an apex is perpendicular to the cutting edge, i.e. every knife which has ANY apex thickness is "dull" from some point of reference. But to a user who needs an edge that cuts a particular medium very well for a very long time, 10 micron might be perfect. Would he prefer <1 micron? Absolutely IFF it lasts as long as he needs it to.

I have absolutely no idea what you mean by the bold bit.

The apex is the foremost point of the knife edge, and nearly every knife edge made of steel is in fact rounded such that the foremost point is on the edge or a curve and the tangent to that point is perpendicular to the cutting edge, i.e. the "apex angle" as measured by the tangent (as some purport to do with convex edges ) would be 90-dps, i.e. perfectly blunt. It is a minor point, just that apex angle isn't what cuts, edge thickness cuts. And in relation to this discussion, an edge > 1 micron at the apex might be "dull" for shaving but is sharp enough for other applications and is in fact preferable IF it remains that thin a great deal longer than the 1 micron edge.

In what form was the AEB-L blade of Gavko "annihilated". Do you feel a similar ground blade in CPM-110V would fair the same or even better?

It wasn't, i didn't write that it was
But i would expect a 110V blade to fair the same, and if it did not I would wonder what hardness or thickness would be required, and how detrimental to performance the necessary alteration would be. Does he have more videos of the same demonstration in the same geometry and hardness on other steels?

I believe it would be similar to this:

"The Custom Phil Wilson knives in M390 (62) and ELMAX (62) are not added to the data, they wouldn't fit into any of the Categories due to the Optimal HT and cutting ability, the difference is off the scale percentage wise so it wasn't added."

If it is ground properly and is heat treated optimally. If that is the case would it out perform many of the listed steel?

Where would you say a knife like this would end up? Photo by cKc Knives.

It would be very nice if AEB-L or 13C26 could perform as high as M390. Care to have a maker submit a blade for testing?

With all due respect. 15 dps is IMO appropriate for a axe and heavy use. Heck, most of the higher wear resistant steels I have used (CPM-M4, M390, S30V) all are stable at 10-12 dps.

The razor blades in Verhoeven's cited paper are 20-dps at the edge. Does that eliminate edge damage? Of course not, because it is NOT the angle that matters, it is the thickness. How thick are those axes back ~1 mm from the apex? How thick are those knives? A separate issue anyway.

But fine grained steel is not limited to fine materials. Fine grained steels show their worth in larger blades splitting bone, chopping trees, etc. Dan Keffeler shows this well with his use of CPM-3V blades ground thin in their geometry.
...
cKc knives again testing AEB-L, thinly ground.
...
I remain of the opinion there are steels to suite all needs. People can decide for themselves what they like but the big difference comes in when someone knows what they are doing with regards to grinding the geometry and heat treat. I would rather take a 1055 blade heat treated and ground well then a CPM-110V, K390, Unobtainium super alloy that glows when you cut that is heat treated like a donkeys rear.

Again, NOT ABRASIVE USE of those steels, tests showing strength and impact resistance that S110V and others might perform just as well in, except that the high-wear steels would be painful to grind to such fashion and those aren't high-wear uses, so why bother? Did the CPM-3V and AEB-L experience no edge damage? I see damage, i.e. fine edge gone. Now show me the damage on S110V. Make me a believer.