What would be Crucible steel contender against BU M390? S110V?

[MobileFireLord]

You have a good point. I've linked some m390 abuse as well as CPM 20cv. Tell me what you think.

http://youtu.be/lNfkY0QHPm4

http://youtu.be/gFzI9U64bjg

It seems M390 and CPM 20CV has near identical listed composition.

Interestingly, S110V has a bit more carbon, more than double Vanadium, addition of Cobalt and Niobium to make it more interesting in producing harder carbide yet small grain. I can see ductility may be lost here, but that compares similar to low carbon steel vs. high carbon steel.

Is it really that BU's 3rd generation powder metal technology leads to higher performance in aiding smaller carbide and uniform consistency of the alloy?

 

[marthinus]

Does Bohler make Elmax ?

Damasteel

Yes Bohler makes Elmax. Not Damasteel.

Google Bohler knife steels. Follow their page link.

 

[marthinus]

I would gladly put a M390 blade at 61-62 and .01 behind the edge up against a 1095 blade at the same hardness and geometry. The M390 blade will be tougher and have much less chipping during hard cutting. The M390 blade may also take more abuse before catastrophic failure.

ELMAX blades when given the correct tempering can absolutely be as tough as steels like 1095 and 01 at their optimum hardness of around 58.

This is from my personal testing and experience. Maybe some other makers can chime in with their experiences but I think it will be pretty similar.

As for M390 vs S30V, I firmly believe M390 is superior in every way, especially in edge stability. Keep in mind M390 is very difficult to HT and production knives may not have the kind of HT and hardness to bring out the best in a high alloy steel. M390 needs a very strict HT regimen and need to be brought to 62 to really shine.

With regards to the bold, I find it hard to believe that a high carbide volume steel like M390/Elmax have greater toughness than a 1095 blade given all things are equal and all are heat treated optimally.

This is from the patent for CPM-3V.

Here is Sandviks table of steels and characteristics.

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

Primary carbides:

"In addition to the main requirements, like high strength and wear re-sistance, tool steels should also possess sufficient toughness to avoid tool failure by cracking or chipping. These failure mechanisms are controlled by the propagation of intrinsic microcracks. The resistance of the mate-rial against growth of an existing crack can be measured conveniently by plane strain fracture toughness tests. Contrary to the bending rupture test,which takes into account both crack initiation and crack growth, plane strain
fracture toughness tests only consider the latter. Crack growth is governed mainly by the content, size and distribution of the primary carbides and the mechanical properties of the matrix. The content of primary carbides is determined by the amount of carbon and carbide forming elements like chromium, molybdenum, vanadium, tungsten and niobium. These elements improve wear resistance and hardness of the material but impair toughness,because of their strong tendency to segregate during solidification." (J. Blaha, C. Krempaszky, E.A. Werner and W. Liebfahrt (2006). CARBIDE DISTRIBUTION EFFECTS IN COLD WORK TOOL STEELS. 6TH INTERNATIONAL TOOLING CONFERENCE. Page 290)

CARBIDE DISTRIBUTION EFFECTS IN COLD WORK TOOL STEELS

 

[chiral.grolim]

With regards to the bold, I find it hard to believe that a high carbide volume steel like M390/Elmax have greater toughness than a 1095 blade given all things are equal and all are heat treated optimally.

...

"In addition to the main requirements, like high strength and wear re-sistance, tool steels should also possess sufficient toughness to avoid tool failure by cracking or chipping. These failure mechanisms are controlled by the propagation of intrinsic microcracks. The resistance of the mate-rial against growth of an existing crack can be measured conveniently by plane strain fracture toughness tests. Contrary to the bending rupture test,which takes into account both crack initiation and crack growth, plane strain
fracture toughness tests only consider the latter. Crack growth is governed mainly by the content, size and distribution of the primary carbides and the mechanical properties of the matrix. The content of primary carbides is determined by the amount of carbon and carbide forming elements like chromium, molybdenum, vanadium, tungsten and niobium. These elements improve wear resistance and hardness of the material but impair toughness,because of their strong tendency to segregate during solidification." (J. Blaha, C. Krempaszky, E.A. Werner and W. Liebfahrt (2006). CARBIDE DISTRIBUTION EFFECTS IN COLD WORK TOOL STEELS. 6TH INTERNATIONAL TOOLING CONFERENCE. Page 290)

CARBIDE DISTRIBUTION EFFECTS IN COLD WORK TOOL STEELS

First off, where is 1095 in that CPM-3v patent chart?

Second, the very next sentence from the paper you quote (in the introduction:

The production of high speed and cold work tool steels via the powder metallurgical (PM) route [1, 2, 3] provides the possibility to use higher contents of carbide forming elements, because segregation is suppressed due to a very high solidification rate (104 to 106 Ks−1) during the atomization process.

And in the conclusion:

The results presented clearly show that cold work tool steels produced via the PM route possess distinctly different fracture toughness K(IC) even though the steels investigated contain roughly the same particle volume fraction and are adjusted to the same macroscopic hardness. A fine distribution is desirable in order to delay crack initiation, but small interparticle distances decrease the resistance of the material against crack propagation. Hence, K(IC) is closely related to the mean interparticle spacing λ and the size of the plastic zone (rp) and, therefore, to the yield strength of the martensitic matrix.

1095 impact toughness at 60 Rc is ~35 J. M390 impact toughness at 60 Rc is 35-40 J. What are we comparing?

 

[Huntsman Knife Co. LLC.]

In my eyes M390 and ELMAX have redefined what stainless steels can do. I don't have any peer reviewed evidence to prove the toughness of M390 or ELMAX compared to carbon steels but from my personal experience they can certainly hang with stuff like 1095 or 01, especially at 60+ RC.

I have a M390 knife at 62 that I've been wailing on for over a year and its yet to take any significant damage. I treat it like an 01 knife in terms of how I use it and it holds up without issue. Batoning, moderate prying, popping out hip bones you name it, it has done it all and lived to tell about it.

 

[Krisztián]

Yes Bohler makes Elmax. Not Damasteel.

Sorry.

 

[RamZar]

Does Bohler make Elmax ?

Yes.

Check out:

• BOHLER-UDDEHOLM: HIGH PERFORMANCE STEEL FOR KNIVES
• BOHLER-UDDEHOLM: KNIFE STEELS FAQ

 

[RamZar]

Composition Comparison Graph For The Knife Steels Crucible S110V, Crucible S90V, Latrobe 20CV, Carpenter CTS-204P, Bohler-Uddeholm M390

 

[chiral.grolim]

In my eyes M390 and ELMAX have redefined what stainless steels can do. I don't have any peer reviewed evidence to prove the toughness of M390 or ELMAX compared to carbon steels but from my personal experience they can certainly hang with stuff like 1095 or 01, especially at 60+ RC.

I have a M390 knife at 62 that I've been wailing on for over a year and its yet to take any significant damage. I treat it like an 01 knife in terms of how I use it and it holds up without issue. Batoning, moderate prying, popping out hip bones you name it, it has done it all and lived to tell about it.

O1 impact toughness @ 58Rc = 41 J, pretty much indistinguishable from M390 & Elmax.

Folks need to understand that Sandvik is marketing razor-blade steel, meant to be VERY thin and used with care. I have yet to see charpy impact values for 13C26 or 12C27 that demonstrate its toughness as "excellent"... but since their scale for "excellent" toughness carbon steels achieve only ~40 J and "poor" toughness achieve ~20 J, I expect their "average" toughness to be ~30 J. Those differences may seem significant when compared to each other, but compared to CPM-3V at ~100 J or S7 at ~160 J, they are all pretty "average".

More on Sandvik's marketing:

Sandvik's fine-carbide stainless knife steels are used for knives, razor blades and cutting components in electric shavers. The combination of high hardness and a fine-carbide structure ensures excellent edge performance. The high hardness of the fine-carbide stainless knife steels provides good edge stability and the high toughness prevents micro-chipping. The small carbides, with an average size of 0.5 microns, allow for unmatched sharpness. A sharp edge should have a radius of 1-2 microns, which is easy to achieve with the small carbides in Sandvik's fine-carbide knife steels.

Understand that, with the proper tools (e.g. diamond hones) there is no issue sharpening high carbide steels as sharp as low carbide steels. Also, a pure carbide ceramic razor blade can achieve 0.005 microns (>200X sharper) and much higher hardness as well, the absolute best in wear resistance and edge stability. But ceramic is low on toughness which is important for most knives (but NOT razor blades).
When folk discuss edge-stability, they are really discussing strength at minimum apex angle geometry - how acute can i make the edge before experiencing unacceptable levels of failure from lateral twists/bending. However, when you can distinguish "high edge stability" from "low edge stability" only at the microscopic level (~20 um) and angles ~20 degrees inclusive in non-abrasive cutting tasks, one wonders why you wouldn't simply raise the apex angle to 30 degrees (recommended by most professionals for a variety of reasons) for an imperceptible loss in cutting efficiency while generally eliminating much of this distinction in edge stability. This all of coarse assumes an appropriate edge-bevel thickness for the task at hand (e.g. 0.005" for careful cutting that avoids lateral stress, >0.015" for harder use).


I would be surprised if CPM-20CV doesn't rate similar to M390 in toughness and edge-retention. Do folk really expect great differences in performance from the same formula made by Bohler vs Crucible?

 

[Huntsman Knife Co. LLC.]

Here's a great example of ELMAX's toughness. I think this confirms that with correct HT ELMAX is as tough as some plain carbon steels. Also I don't think S30V could at the same hardness could pass that test with such little damage.

https://www.youtube.com/watch?v=H15hvfa8bIQ

 

[chiral.grolim]

Here's a great example of ELMAX's toughness. I think this confirms that with correct HT ELMAX is as tough as some plain carbon steels. Also I don't think S30V could at the same hardness could pass that test with such little damage.

https://www.youtube.com/watch?v=H15hvfa8bIQ

Hmm, 0.030" behind the edge, 20-dps... that isn't really thin, pretty standard actually. But we already know the S30V from Chris Reeve Knives couldn't handle that

 

[pnsxyr]

To my understanding, the "generation" labeling of Crucible's, Bohler's, and Carpenter's PM processes are a little misleading in a sense that these different generations are just different, rather than definitive improvements.

I am yet to use any steel I think I could compare to M390's unusual properties, but I have not used 20 CV. It's wear resistance is just insane, and unlike many other steels, it holds that 'scary sharp' for a very long time even with extensive usage. It's corrosion resistance is exceptional, it's quite a tough steel with thin angles, and it's not as hard to sharpen as many other steels with crazy high wear resistance. I've come to personally really prefer it over S90V and S110V.

I think S35VN is comparable to ELMAX though. Both of those steels are unusually tough when the heat treatment is done right.

 

[MobileFireLord]

I would state that "3rd generation" label of M390 is being compare to Bohler-Udderholm 's powder metal line ups. I'm certain that Neither Crucible nor BU shares details of powder size.

Since BU advertises openly about 3rd generation with "super clean" and smaller particle size, they have improved drastically on pre furnace ingredients particle size and elimination of undesirable materials.

I haven't tested to compare between 20CV vs. M390 in same blade geometry and heat treatment, so I too can not say definitively. Many of the test that has been conducted by members of this forum seems to indicate M390 is one of the best stainless steel and that seems to have more manufacture seems to use it.

I'm sure as many of you buy knives by first chose the ergonomics and particular blade shape. Within that parameter, I would chose the steel I like. In folding knife category, I enjoy Benchmade and Spyderco who are making knives in that fashion.

MFL

 

[MobileFireLord]

Composition Comparison Graph For The Knife Steels Crucible S110V, Crucible S90V, Latrobe 20CV, Carpenter CTS-204P, Bohler-Uddeholm M390

Thank you for the visual, RamZar! It makes clear understanding of ingredients that shows the difference. It seems Crucible choses more vanadium to minimize carbide grain, and Bohler Udderholm and carpenter (Latrobe) enhances through chromium.

AS S110V is advancement of S90 to be more corrosion resistant, molybdenum contents are tripled. Also Niobium and Cobalt are known enhancement in hard carbide former as well as grain size restrictor. Those are wear resistant yet would not hinder sharpen ability. Of cause using diamond sharpener does make it easy to sharp, but stropping may be still time consuming.

 

[pnsxyr]

Thank you for the visual, RamZar! It makes clear understanding of ingredients that shows the difference. It seems Crucible choses more vanadium to minimize carbide grain, and Bohler Udderholm and carpenter (Latrobe) enhances through chromium.

AS S110V is advancement of S90 to be more corrosion resistant, molybdenum contents are tripled. Also Niobium and Cobalt are known enhancement in hard carbide former as well as grain size restrictor. Those are wear resistant yet would not hinder sharpen ability. Of cause using diamond sharpener does make it easy to sharp, but stropping may be still time consuming.

Side question...why is it that I find S110V to be much easier to sharpen S90V? Is it just because the S110V knives I use have blades that are easier to work with, or is S110V actually easier to sharpen?

 

[marthinus]

First off, where is 1095 in that CPM-3v patent chart?

Good question. I do not know, maybe contact Crucible and ask them? As with most steels it is difficult to match steels across groups.

In his book Steel Heat Treatment Metallurgy and Technologies, George E. Totten warns against this and classifies steels into an array of categories such as Molybdenum high-speed steels, High-carbon, high-chromium cold-work steels, Shock-resisting steel, Water-hardening steels, High Strength Low Alloy steels etc. He compares each group and some of the steels in that group giving their Resistance to Decarburization, Hardening Response, Amount of Distortion, Resistance to cracking, Approximate Hardness, Machinability, Toughness, Resistance to Softening and resistance to wear.

Second, the very next sentence from the paper you quote (in the introduction:



And in the conclusion:

I am glad you showed the conclusion and very next sentence, because, the advancements in Powdered Technology is not what I am arguing against.
The advancements of Powdered have been well documented. From the following article it gives a nice summary:

Summarizing, the advantages of PM tool steels are a lot and they interest both the tool manufacturer, as well as the end user. In particular, for the End User:
• Higher Alloy Grades Available
• Improved Wear Resistance
• Improved Toughness (less chipping)
• Consistent Tool Performance
• Good Grindability (on resharpening)

Whilst for the Tool Manufacturer:
• Consistent Heat Treat Response
• Predictable Size Change on Heat Treat
• Excellent, Stable Substrate for Coatings
• Excellent Grindability
• Improved Machinability (w/sulfur enhancement)
• Efficient Wire EDM Cutting

M. Rosso, D. Ugues, M. Actis Grande, Journal of Achievements in Materials and Manufacturing Engineering, 2006, The challenge of PM tool steels for the innovation, VOLUME 18, ISSUE 1-2, September–October 2006.

If we look at the below table from Steel Heat Treatment Metallurgy and Technologies, George E. Totten the following table shows the improvement of one steel through different processes. Note this is one steel and there is still no cross comparison of steel groups. Once again one can see that through the different processes and advancements one can improve upon the ingot version. One can also see that the smaller the carbide size is the better the toughness, grindability and bend strength, but lower the wear resistance slightly.

George E. Totten also states: “Toughness properties are influenced strongly by the microstructure, and they show improvement with a more homogeneous microstructure. Finer spheroidized carbides also improve toughness.” (Page 686).

Once again, I am not arguing about the advancements of PM process and its improvement over the ingot version.

I am however stating that toughness is influenced by carbide size and volume. As I showed in the graph from the patent information there is a direct relationship with Carbide volume and toughness. The lower the carbide volume the higher the toughness will be.

Let us examine the Patent graph for CPM-3V again.

Since one cannot state a bunch of BS in patent information or a patent would not be granted Crucible has to state metallurgical truth. So, what is stated in the patent information.

[0035] An important aspect of the invention is illustrated in Figure 3 which shows the Charpy C-notch impact test results versus total carbide volume for the PM tool steels that were heat treated to 60-62 HRC, as well as test results obtained for several conventionally produced tool steels at about the same hardness. The results show that the toughness of the PM tool steels decreases as the total carbide volume increases, essentially independent of carbide type……
In alloys PM 10V, PM 15V, and PM 18V, which similar to the alloy of the invention contain only MC-type carbides but at a volume level substantially above that of the invention alloy, impact toughness is drastically reduced over that achieved in accordance with the invention. Hence, to achieve the results of the invention, not only must the primary carbides be MC-type carbides, but the volume thereof must be within the limits of the invention, e.g., 4 to 8 percent by volume.

Page 12 of patent.

Now, let us put carbide size into perspective. Here is a pdf from metallurgist R. Landes showing the carbide structure of O1, D2, S90V and Tolonite. If one folds the PDF as recommended one will see that the smaller the carbide content the finer the edges can be and the higher the cutting quality and performance will be.

http://www.hypefreeblades.com/files/schneiden.pdf

Some pictures showing the carbide size of different steels:

12C27 in micro structure.

12c27 at the edge

Coarse carbide structure at the edge

Here is N690, similar to VG-10.

Here we can see CPM 154

Here is normal Ingot 154CM

So given all of the above and the information I have read and have referenced many times I firmly believe that a high carbide steel such as CPM-110V, M390 etc cannot have the same toughness as lower carbide volume and size steels. Please provide referenced data or research papers if you do not agree, not materials pdf's as those are for marketing.

We have had similar discussions before.

http://www.bladeforums.com/forums/s...n-Edge-Retention-cutting-5-8-quot-rope/page75

http://www.bladeforums.com/forums/s...n-Edge-Retention-cutting-5-8-quot-rope/page76

1095 impact toughness at 60 Rc is ~35 J. M390 impact toughness at 60 Rc is 35-40 J. What are we comparing?

Good question. As I stated when we had the previous back and forth:

One cannot go on Charpy tests data given in datasheets alone IMO. Why? Because there is a lot of data not given. Here is a post I did:

Unfortunately in most steel data sheets available to us there is no specifications by many manufacturers and one is left with a few questions.

Here is an article about fracture toughness and orientation:

EducationResources, Community College, Materials, Mechanical, Fracture Toughness

Orientation
The fracture toughness of a material commonly varies with grain direction. Therefore, it is customary to specify specimen and crack orientations by an ordered pair of grain direction symbols. The first letter designates the grain direction normal to the crack plane. The second letter designates the grain direction parallel to the fracture plane. For flat sections of various products, e.g., plate, extrusions, forgings, etc., in which the three grain directions are designated (L) longitudinal, (T) transverse, and (S) short transverse, the six principal fracture path directions are: L-T, L-S, T-L, T-S, S-L and S-T.

From the book:

Metallurgy of Steel for Bladesmiths & Others who Heat Treat and Forge Steel - By John D. Verhoeven (2005)

On Page 53

"The orientations of two Charpy impact bars are also shown.
Notice that in the transverse bar the elongated inclusions will run parallel to the base of
the V-notch while in the longitudinal bars they will run at right angles to the base of the
V-notch. Brittle failure occurs by cracks being opened up by the triaxial stresses
generated at the base of the V-notch. Now consider the
effects of the elongated inclusions. When the inclusions
lie parallel to the V-notch baseit is possible to have an
inclusion lying along the entire base of the V-notch. But
when the inclusions lie at rightangles to the base of the
V-notch an inclusion will pass the base of the notch at
only one point. Hence, the inclusions will enhance crack
formation much more effectively for the transverse bar
orientations where they lie parallel to the base of the V-
notch. Charpy data on rolled sheet containing
elongated sulfide inclusions give impact energies of
around 44 ft-lbs for longitudinal bars and only 15 ftlbs for transverse bars. The data provide dramatic
evidence illustrating how elongated inclusions
reduce the transverse toughness of wrought steels."


Another that seems to discuss orientation:
Suranaree University of Technology

• Longitudinal (B)
shows the
best energy absorption because
the crack propagation is across
the fibre alignment.

• Transverse (C)
gives the worst
energy absorption because the
crack propagates parallel to the
rolling direction

END.

It is also important to remember that one cannot just compare different steel categories to each other. Even similar steel categories such as in the Shock-resisting steels can have different values because of the variables I mentioned above and different heat treatment.

Now, as I posted earlier:

Grain size and its affects on strength

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

The same holds true for primary carbides:

"In addition to the main requirements, like high strength and wear re-sistance, tool steels should also possess sufficient toughness to avoid tool failure by cracking or chipping. These failure mechanisms are controlled by the propagation of intrinsic microcracks. The resistance of the mate-rial against growth of an existing crack can be measured conveniently by plane strain fracture toughness tests. Contrary to the bending rupture test,which takes into account both crack initiation and crack growth, plane strain
fracture toughness tests only consider the latter. Crack growth is governed mainly by the content, size and distribution of the primary carbides and the mechanical properties of the matrix. The content of primary carbides is determined by the amount of carbon and carbide forming elements like chromium, molybdenum, vanadium, tungsten and niobium. These elements improve wear resistance and hardness of the material but impair toughness,because of their strong tendency to segregate during solidification." (J. Blaha, C. Krempaszky, E.A. Werner and W. Liebfahrt (2006). CARBIDE DISTRIBUTION EFFECTS IN COLD WORK TOOL STEELS. 6TH INTERNATIONAL TOOLING CONFERENCE. Page 290)

CARBIDE DISTRIBUTION EFFECTS IN COLD WORK TOOL STEELS

Vanadium affects described in patent information:

IMO if there is too large primary carbides you wont have the same strength and toughness you can have in a high strength low alloy steel. If what you want is wear resistance then IMO buy a knife with the properties and heat treat for high wear resistance, but from everything I have read my opinion is that you cannot expect a high wear resistant steel to have the same resistance to impact or deformation as lower alloy, fine grained and small carbide steels.

 

[MobileFireLord]

Side question...why is it that I find S110V to be much easier to sharpen S90V? Is it just because the S110V knives I use have blades that are easier to work with, or is S110V actually easier to sharpen?

I too find that S110V is easier to sharpen than S90V, but not with S30V. From listing of alloy content, I have noted three metals that it gives additional edge (no pun intended)

Niobium: It is also added to S35VN. You may notice that S35VN is designed to retain edge retention, but increase workability than S30V. What niobium does is creating harder carbide with smaller and well distributed. Also noted that S110V contains more carbon and vanadium. Carbon is the source of carbide, and increased vanadium makes carbide grain to be smaller.

Cobalt: As the name suggests, adding this metal will make the alloy harder and improves heat treatment temperature. SO, with same hardness, the alloy it contains "performs" better.

Manganese: It adds toughness and wear resistance. I am surprised S90V does not contain it.

So, S110V has harder carbide to resist wear, yet smaller carbide makes it easier to work with.

 

[chiral.grolim]

Good question. I do not know, maybe contact Crucible and ask them? As with most steels it is difficult to match steels across groups.

No, it isn't, which is why I gave the value for 1095 that is NOT included in the patent chart that you used to argue:

I find it hard to believe that a high carbide volume steel like M390/Elmax have greater toughness than a 1095 blade given all things are equal and all are heat treated optimally

"Heat treated optimally" for what? 1095 is "spring steel" that can be VERY tough if given a longer/hotter temper but this compromises apex strength. If left hard for cutting strength, it's toughness is reduced to the value i indicated.

the advancements in Powdered Technology is not what I am arguing against.

The carbide volume of Elmax and M390 is significantly higher than that of 1095. You do not believe that toughness could possibly be the same between PM high-carbide steels and low carbide ingot steels based on data regarding high carbide ingot steels, despite being able to cite specific articles indicating that improved toughness from the PM process. You posted patent information describing the deleterious effects of increased vanadium in INGOT steel which the PM process described in the very next paragraphs MITIGATES:

It is accordingly a primary objective of the present invention to provide pre-alloyed high-vanadium cold work tool steel particles for use in powder-metallurgy production of cold work tool steel articles wherein amounts of MC-type vanadium carbides may be present as a dispersion in the alloy matrix in amounts greater than heretofore possible to achieve improved wear resistance, while retaining sufficient toughness and grindability.

That is EXACTLY what the PM process is all about - making high-carbide steels as tough as low carbide steels. Charpy tests indicate this to be successful. You have posted information supporting it. So why is it hard to believe?

One can also see that the smaller the carbide size is the better the toughness, grindability and bend strength, but lower the wear resistance slightly.

Yes, all of which makes perfect sense. Again, the MOST wear resistant blade material is PURE carbide. An ingot steel with very large carbides at the surface (or the meeting of surfaces, i.e. an apex) is presenting a pure-carbide edge to the medium, hence higher wear-resistance than smaller carbides more evenly distributed. Landes' fold-over image for D2 demonstrates this exceptionally well - if you sharpened the apex down to that carbide running the entire width of the diagram, that would be an exceptionally wear-resistant edge! Of coorse the weaker bond between the carbide and the matrix would make it prone to failure if impact or lateral forces dislodged that carbide, which is the reason for implementing PM, to be able to present a similar volume of carbide at the surface but enhance strength and toughness dramatically.

I am however stating that toughness is influenced by carbide size and volume. As I showed in the graph from the patent information there is a direct relationship with Carbide volume and toughness. The lower the carbide volume the higher the toughness will be.

[0035] An important aspect of the invention is illustrated in Figure 3 which shows the Charpy C-notch impact test results versus total carbide volume for the PM tool steels that were heat treated to 60-62 HRC, as well as test results obtained for several conventionally produced tool steels at about the same hardness. The results show that the toughness of the PM tool steels decreases as the total carbide volume increases, essentially independent of carbide type...

Note the wording as well as the chart. Crucible is comparing toughness and carbide volume between PM steels but includes a couple of others for reference. Look at A2 vs CPM-3V, or compare D2 vs CPM-D2, 154CM vs CPM-154 - instances of the same carbide volume but dramatically different toughness due to carbide size and distribution. I asked earlier about where 1095 fell on the chart to see if you could place it in carbide volume given it's Charpy impact values at similar hardness. http://zknives.com/knives/steels/steelgraph.php?nm=1095,A2&ni=360,11

... R. Landes showing the carbide structure of O1, D2, S90V and Tolonite. If one folds the PDF as recommended one will see that the smaller the carbide content the finer the edges can be and the higher the cutting quality and performance will be.

Again, PURE carbide forms the FINEST edges, 200X finer than any steel can achieve. Images of poorly formed high/large carbide edges may suggest that it requires higher skill or better abrasives to achieve as fine of an apex (e.g. low micron diamond particles) but such high carbide levels do not prevent the possibility of achieving such fine edges or even finer edges since the harder carbides have the strength in themselves to hold a thinner apex than a softer matrix and martensite (provided you do not chip them out).

I firmly believe that a high carbide steel such as CPM-110V, M390 etc cannot have the same toughness as lower carbide volume and size steels. Please provide referenced data or research papers if you do not agree, not materials pdf's as those are for marketing.

I have posted it before: http://www.kau.se/sites/default/files/Dokument/subpage/2010/02/26_349_359_pdf_19432.pdf

Your information about fracture toughness in orientation has already been answered elsewhere but i will state again it is irrelevent since we are always comparing longitudinal impact values, never transverse which would be dramatically lower for all and would reveal itself constantly in regular knife use given how low the values are.

"Crack growth is governed mainly by the content, size and distribution of the primary carbides and the mechanical properties of the matrix. The content of primary carbides is determined by the amount of carbon and carbide forming elements like chromium, molybdenum, vanadium, tungsten and niobium. These elements improve wear resistance and hardness of the material but impair toughness,because of their strong tendency to segregate during solidification."

you quoted the same thing in your last post to which I responded with the very next sentence and the conclusion in the paper:

The production of high speed and cold work tool steels via the powder metallurgical (PM) route [1, 2, 3] provides the possibility to use higher contents of carbide forming elements, because segregation is suppressed due to a very high solidification rate (104 to 106 Ks−1) during the atomization process...

The results presented clearly show that cold work tool steels produced via the PM route possess distinctly different fracture toughness K(IC) even though the steels investigated contain roughly the same particle volume fraction and are adjusted to the same macroscopic hardness. A fine distribution is desirable in order to delay crack initiation, but small interparticle distances decrease the resistance of the material against crack propagation. Hence, K(IC) is closely related to the mean interparticle spacing λ and the size of the plastic zone (rp) and, therefore, to the yield strength of the martensitic matrix.

You keep citing information on the diminished toughness of high-carbide INGOT steel from papers/patents demonstrating the increased toughness of high-carbide PM-steels as a reason for doubting the increased toughness of high-carbide PM steels? I am confused by this.

IMO if there is too large primary carbides you wont have the same strength and toughness you can have in a high strength low alloy steel. If what you want is wear resistance then IMO buy a knife with the properties and heat treat for high wear resistance, but from everything I have read my opinion is that you cannot expect a high wear resistant steel to have the same resistance to impact or deformation as lower alloy, fine grained and small carbide steels.

P/M steels like M390 provide high toughness, high strength, small carbides, AND much higher wear resistance than their low-carbide ingot counterparts. But they are also more expensive to produce.
Again, what are the impact values for 13C26 (AEB-L) or 12C27 or 1095 or O1 or 52100 - small carbide, low-wear razor-blade steels? Even Sandvik's marketing data suggests they are not tougher than M390 and Elmax.
But they are cheaper.

I anxiously await an English version of Landes' work so i can finally read his methods for edge-stability. From what I've read of his posting on hypefreeblades, he tested lateral strength of apices on the micron scale - similar to an edge-flex test but more controlled - to find how low different steels at high hardness could go in apex-angle prior to failure, proceeding below the 30-degrees required to endure the stresses most common in everyday use of a utility knife. I think it would be far more useful to know how thin different steels can be taken behind a 30-degree edge while maintaining sufficient strength for everyday use. i already know that 0.005" is too thin for AEB-L carving oak

 

[marthinus]

No, it isn't, which is why I gave the value for 1095 that is NOT included in the patent chart that you used to argue:

Reference please. We do not know the thickness, hight, HRC depth of cut for test.

The carbide volume of Elmax and M390 is significantly higher than that of 1095. You do not believe that toughness could possibly be the same between PM high-carbide steels and low carbide ingot steels based on data regarding high carbide ingot steels, despite being able to cite specific articles indicating that improved toughness from the PM process. You posted patent information describing the deleterious effects of increased vanadium in INGOT steel which the PM process described in the very next paragraphs MITIGATES:

PM process improves upon the ingot version correct, however PM process does not mitigate the carbide volume. So no matter the size of the carbides there will always be the same amount of carbide volume in the Ingot and PM steels. Therefore, no matter the process, due to the same amount of carbide volume toughness will always be greater in the less carbide volume steel.

That is EXACTLY what the PM process is all about - making high-carbide steels as tough as low carbide steels......So why is it hard to believe?

The why do we not see high carbide PM steels replacing steels such as S7 in jack hammer bits? I fact, if you read The following research they found under heavy loads steels such as S7 had better wear resistance than D2 and CPM-M4.

Once again. Comparing steels beyond it classified class becomes sketchy, especially if not all information is disclosed as in hardness, tempering program, specimen size, orientation etc . Parameters change hence you get Molybdenum high-speed steels, High-carbon, high-chromium cold-work steels, Shock-resisting steel, Water-hardening steels, High Strength Low Alloy steels etc.

Yes, all of which makes perfect sense. Again, the MOST wear resistant blade material is PURE carbide. An ingot steel with very large carbides at the surface (or the meeting of surfaces, i.e. an apex) is presenting a pure-carbide edge to the medium, hence higher wear-resistance than smaller carbides more evenly distributed. Landes' fold-over image for D2 demonstrates this exceptionally well - if you sharpened the apex down to that carbide running the entire width of the diagram, that would be an exceptionally wear-resistant edge! Of coorse the weaker bond between the carbide and the matrix would make it prone to failure if impact or lateral forces dislodged that carbide, which is the reason for implementing PM, to be able to present a similar volume of carbide at the surface but enhance strength and toughness dramatically.

I agree with you except that lateral or impact forces are not the only method of dislodging the carbide. At a certain point the matrix cannot hold the carbide any more and then the carbide will just fall out. More commonly known as micro chipping.

What do you consider pure carbide? There are about several when we talk about steel. Also listed in George E. Totten's book.

Note the wording as well as the chart. Crucible is comparing toughness and carbide volume between PM steels but includes a couple of others for reference. Look at A2 vs CPM-3V, or compare D2 vs CPM-D2, 154CM vs CPM-154 - instances of the same carbide volume but dramatically different toughness due to carbide size and distribution. I asked earlier about where 1095 fell on the chart to see if you could place it in carbide volume given it's Charpy impact values at similar hardness. http://zknives.com/knives/steels/steelgraph.php?nm=1095,A2∋=360,11

The graph aslo indicates how higher carbide volume steels do not have the same toughness as A2 or D2 ingot but still has the advantages of all the PM processes. Yet they are not as tough. Also note. CPM-3V has a carbide volume of 4-8% according to its patent information. Less than that of CPM-154, 440C etc so it should be tougher.

I am not going to do the math to determine carbide volumes. I am far too busy with personal matters. However, by al means, you can do it on your own time.

I have posted it before: http://www.kau.se/sites/default/files/Dokument/subpage/2010/02/26_349_359_pdf_19432.pdf

PM PLASTIC MOULD STEELS, nice comparison of the group. Not trying to compare beyond its classification like we as knife nuts tend to do.

Your information about fracture toughness in orientation has already been answered elsewhere but i will state again it is irrelevent since we are always comparing longitudinal impact values, never transverse which would be dramatically lower for all and would reveal itself constantly in regular knife use given how low the values are.

Do you have a reference that longitudinal impact values are always compared?

You keep citing information on the diminished toughness of high-carbide INGOT steel from papers/patents demonstrating the increased toughness of high-carbide PM-steels as a reason for doubting the increased toughness of high-carbide PM steels? I am confused by this.

Once again, I am not arguing against the advancements of the PM process, however, if you look at the patent information again CPM-10V and 18V are steels done through the CPM process with higher carbide volume, still better distribution and less segregation than its ingot version, yet it does not have the same toughness as A2, D2 or CPM-3V that has the lowest carbide volume in the patent graph.

I anxiously await an English version of Landes' work so i can finally read his methods for edge-stability. From what I've read of his posting on hypefreeblades, he tested lateral strength of apices on the micron scale - similar to an edge-flex test but more controlled - to find how low different steels at high hardness could go in apex-angle prior to failure, proceeding below the 30-degrees required to endure the stresses most common in everyday use of a utility knife. I think it would be far more useful to know how thin different steels can be taken behind a 30-degree edge while maintaining sufficient strength for everyday use. i already know that 0.005" is too thin for AEB-L carving oak

I think learning another language will be faster than waiting for a publisher to publish a research piece in another language.

How is this for 14C28N at 0.004

[video=youtube;057CNdALWCA]https://www.youtube.com/watch?v=057CNdALWCA[/video]

 

[Huntsman Knife Co. LLC.]

Sorry to resurrect this thread but I spoke to Jessica at AKS yesterday and she informed me that CTS 204P shows the same toughness as M390 despite the difference in PM processes. Jim's testing has shown comparable edge retention as well.

She also said that 204P is looking like it will be easier to supply and doesn't come coated in a protective stainless canister which cuts down price so I am expeciting it to become more popular than M390 as time goes on. I think I will be making the switch to 204P with these things in mind.

Its an exciting time to be a steel junkie thats for sure :thumbup: