Which Steel Has the Best Edge Retention?

marchone said:
This raises two questions to a user. What is a good blade geometry? And how can the consumer achieve it?
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An article in an old Irish agricultural journal discussing axes phrased it something along the lines of "edges of cutting tools should generally be as thin as is consistent with requisite strength", and that summarizes things quite nicely in my opinion.

One need simply identify what the tool needs to be capable of withstanding, and select a geometry as thin as the given steel and heat treatment are able to support in use. Of course, steel and heat treatment play into what the practical minimum dimensions are, and the skill of the user and context of use determine the kind of forces it has to be able to withstand. You just keep on asking "what determines _____?" and keep walking it back until you get down to the roots guiding the design. And good design is generally an iterative process because altering one variable impacts several others at once, so you just have to keep going around and around until everything is optimized relative to everything else. :)
 
FortyTwoBlades said:
An article in an old Irish agricultural journal discussing axes phrased it something along the lines of "edges of cutting tools should generally be as thin as is consistent with requisite strength", and that summarizes things quite nicely in my opinion.

One need simply identify what the tool needs to be capable of withstanding, and select a geometry as thin as the given steel and heat treatment are able to support in use. Of course, steel and heat treatment play into what the practical minimum dimensions are, and the skill of the user and context of use determine the kind of forces it has to be able to withstand. You just keep on asking "what determines _____?" and keep walking it back until you get down to the roots guiding the design. And good design is generally an iterative process because altering one variable impacts several others at once, so you just have to keep going around and around until everything is optimized relative to everything else. :)
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Yes!

IMO, this is why it's so important to be very specific about different cutting use cases and the degree to which they are or are not modeled by a particular testing methodology. Or conversely, when discussing a testing methodology, it's super important to clearly describe what sort of cutting use cases the testing is well aligned with and which ones are not well modeled by the test.

Larrin, you were correct, you had mentioned some of the use case issues I raised. Take the suggestion as an intended help, which you're free to ignore obviously... I think several of your blog posts could be strengthened by spending more time up front discussing use case applicability and limitations of the test in question, as opposed to sprinkling that commentary across the document. IMO, it might help mitigate some of the "real world" complaints you've seen in this thread.
 
As far as higher-carbide steels "losing" their edge faster, it's all in what you consider "sharp" and how it got there. My S110V steel will lose its bite just sitting there, whereas something like my Rex45 or 154CM stays scary for seemingly forever if not used. On the other hand, the S110V will stay remain usable for way longer than 154CM if I were to start processing cardboard.
 
Cypress said:
As far as higher-carbide steels "losing" their edge faster, it's all in what you consider "sharp" and how it got there. My S110V steel will lose its bite just sitting there, whereas something like my Rex45 or 154CM stays scary for seemingly forever if not used. On the other hand, the S110V will stay remain usable for way longer than 154CM if I were to start processing cardboard.
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There is a theory that unless you use diamonds to sharpen these high-wear steels, you will get a weak edge that leaves the carbides high and round, while wearing down the matrix. Using diamonds avoids this problem.

I use diamonds and don't see this problem. My S110V does not lose its edge "just sitting there." But others report that edges not sharpened using diamonds are weak and fail quickly, giving the impression that the edge loses it's keenness for no reason.

There is a thread in the Maintenance section that talks about this issue and gives evidence.
https://www.bladeforums.com/threads/high-vanadium-carbide-tear-out-questions.1626135/
 
154CM has less carbide volume than S110V (17.5 vs 22%) but it is far from a low carbide steel and its carbides are much larger than S110V.
 
Larrin said:
154CM has less carbide volume than S110V (17.5 vs 22%) but it is far from a low carbide steel and its carbides are much larger than S110V.
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The smaller vanadium carbides are only helpful if the sharpening methods can sufficiently work them. I have much less trouble working the larger, but softer, chromium carbides in 154cm.

I'll echo what T Twindog said in that diamonds are a must for S110V sharpening (not the first time I've said this on BF, won't be the last). Since I only use diamonds at the stropping phase, it makes sense that my S110V "dulls" rather easily.
 
Was anyone surprised by the AEBL at high hardness with low geometry?

AEBL at 62rc with a 12dps edge angle and 6% Cr7C3 Chromium Carbides.

−157+15.8×62−17.8×24+11.2×6
=462

Elmax at 60rc with a 15dps edge angle.
With 16% M7C3 Chromium Vanadium Carbides and 2% MC type Vanadium Carbides.

−157+15.8×60−17.8×30+14.6×16+26.2×2
=543

S30V at 60rc with a 15dps edge angle with 10.5% M7C3 Chromium Vanadium Carbides and 4% MC type Vanadium Carbides

−157+15.8×60−17.8×30+14.6×10.5+26.2×4
=515

S35VN at 60rc with a 15dps edge angle with 10.5% M7C3 Chromium Vanadium Carbides and 3.5% MC type Vanadium, Niobium rich carbides

−157+15.8×60−17.8×30+14.6×10.5+26.2×3.5
=502

CPM154 at 60rc with a 15dps edge angle 17.5% Cr7C3 chromium carbides

−157+15.8×60−17.8×30+11.2×17.5
=453

Now if it was Nitro V, that has the same composition as AEBL, but small additions of vanadium and Nitrogen to increase the working hardness to 64rc with a 1900f Austenizing, -300 cryo after quenching and a 300f temper x2

It would look like this

Nitro V at 64rc with a 12dps edge angle and if it also forms the same 6% CrC3 Chromium Carbide.

−157+15.8×64−17.8×24+11.2×6
=494

While the other steels can be skyrocketed to higher values by also doing the same thing. AEBL is stable at that hardness especially for kitchen knives and wood carving tools.


Lots of fun to play with the formula.

Especially as a maker that uses lots of different steels



RqQvy3C.png
 
AEBL at 60rc with a 30dps wasn't as exciting though.

−157+15.8×60−17.8×30+11.2×6
=324
 
This guy makes a good rebuttal for Gerber's 7Cr17MoV...


For a budget steel that's pretty darn good
 
Had a video discussion with Larrin Larrin about this article on wear resistance.

We discussed what CATRA testing is.

A brief primer on Carbides.

What the most important factor is for slicing edge rentention.

Carbide Size importance.

Explanation of Predicting CATRA with regression formula to "sandbox" steel performance.

Other factors for edge holding.

What steel cuts the longest?

Enjoy.

 
It's no surprise that CPM Rex 121 is the king of slicing edge rentention.

The combination of hardness and carbide volume puts it as the last stop in steel before moving into just carbide metals.

It is by far the most difficult material I've worked with to date.

Lots of abrasives were needed to make.

This knife is at 70hrc.

wKVrI0O.jpg
 
DeadboxHero said:
It's no surprise that CPM Rex 121 is the king of slicing edge rentention.

The combination of hardness and carbide volume puts it as the last stop in steel before moving into just carbide metals.

It is by far the most difficult material I've worked with to date.

Lots of abrasives were needed to make.

This knife is at 70hrc.

wKVrI0O.jpg
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I can't believe you actually got that thing hand-rubbed LOL

did you use diamond lapping film?
 
Sometimes I wonder if certain people impart too much importance to edge retention...
Sharpening basic steels is wuick and easy and they don’t dull that quickly in my experience

What are you guys cutting that requires such high carbide steels?
 
It's nice to sharpen when you want to and not because you have to. It can be annoying to stop and sharpen because your knife is blunted down and sliding during the cut in the middle of a given task.

In a world of fidget spinners, gaudy frame lock folders, and prybar cold chisels shaped like knives, there is room for folks that appreciate edge performance.

Revolverrodger said:
Sometimes I wonder if certain people impart too much importance to edge retention...
Sharpening basic steels is wuick and easy and they don’t dull that quickly in my experience

What are you guys cutting that requires such high carbide steels?
Click to expand...
 
Revolverrodger said:
Sometimes I wonder if certain people impart too much importance to edge retention...
Sharpening basic steels is wuick and easy and they don’t dull that quickly in my experience

What are you guys cutting that requires such high carbide steels?
Click to expand...
I think it's a 'because you can' thing. Why does one need a car that can go 200+ MPH?
 
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