“Toughness, edge retention, corrosion resistance—pick two.” Is this still the case today?

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DangerZone98

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Dec 7, 2019
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In the past, I read somewhere here on BF that we could ‘only’ have two of the big three mentioned in the title, as a very loose rule of thumb. Do you agree with this statement or is it utter rubbish? Perhaps modern steels today offer a great balance among the three?
 
You can balance properties but you don’t get to pick two. Toughness and wear resistance are opposing properties so you don’t get to pick both. Powder metallurgy and improved steel design gave a higher combination of the two than older steels but it’s still a tradeoff.
 
Larrin said:
You can balance properties but you don’t get to pick two. Toughness and wear resistance are opposing properties so you don’t get to pick both. Powder metallurgy and improved steel design gave a higher combination of the two than older steels but it’s still a tradeoff.
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Thank you for the response. Never really thought of toughness and wear resistance as opposing properties, but I’ll keep that in mind from now on. For real life purposes in my case, I’d say it’s nice to have a good balance of the three.
 
I’d say no. I guess it depends on how much of each property you need, but something like Cruwear has a good balance. Good edge retention, pretty tough, and decent corrosion resistance. I value well- rounded steels in my collection, and Larrin’s Magnacut has supplanted all else for me. It’s plenty tough for anything I do with a knife, I find the edge retention to be very good, and I haven’t gotten it to stain even when trying to do so on purpose. For folders and small fixed blades, it’s as perfect as it gets imo, at least until Larrin comes up with something else lol. Plus, it’s really not hard to sharpen, even at 63-64 hrc.

After my first few Magnacut blades, the composition of my collection underwent an overhaul. I sold most of my knives and started tracking down comparable knives in MagnaCut. I’ve been very pleased. I don’t know that I’d want a sword made of Magnacut (though Dawson makes them), but I have no use for a sword anyway.
 
You didn't mention sharpenability, that's the other piece to the puzzle.

There are well balanced steels available.
We all have favorites, yet in the end my Grandpa's case folder still does the job just fine.
 
DangerZone98 said:
Thank you for the response. Never really thought of toughness and wear resistance as opposing properties, but I’ll keep that in mind from now on. For real life purposes in my case, I’d say it’s nice to have a good balance of the three.
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to expand on that a little bit, in simple terms, and Larrin Larrin can correct me where I'm wrong - generally edge retention = harder steel which in turn generally means more brittle. brittle reduces toughness
 
For my purposes , corrosion resistance and edge retention are my most important considerations.

And I’m curious about Magnacut. I have yet to try it out.
 
On the perspective of harder the steel, the more wear resistance it gets, but less tough it becomes, they are indeed opposite in relative term.
If steel A has more toughness, steel B has more wear resistance. Then they make steel B(PM), which still has it wear resistance of B, but close to match the toughness of A, then it does kind of get both.
However, steel B(PM) has more wear resistance potential, which is again lead to lower toughness, but then we have moved to a bigger scale/chart.
I hear something like K490 has some pretty good wear resistance and toughness. I would like Larrin to test it out.
 
Larrin said:
You can balance properties but you don’t get to pick two. Toughness and wear resistance are opposing properties so you don’t get to pick both. Powder metallurgy and improved steel design gave a higher combination of the two than older steels but it’s still a tradeoff.
Click to expand...
Is wear resistance and edge retention the same thing? Also what is the reason for toughness and wear resistance being directly opposing properties? Not challenging what you said, just want to learn more.
 
Metamorph said:
Is wear resistance and edge retention the same thing? Also what is the reason for toughness and wear resistance being directly opposing properties? Not challenging what you said, just want to learn more.
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Toughness is basically how much kinetic energy the steel can absorb without breaking. Kinetic energy is absorbed by the structure of the steel being deformed, so the more easily the steel moves without breaking (ductility) and the more energy needed to deform the steel (strength), the tougher it will be. But the more easily the steel moves, the faster your edge will warp or be pushed in.
 
Are toughness and edge retention really and always the opposite of each other? When cutting very hard materials, a tougher steel might help the integrity of the edge than a less tougher steel, no? That is, big chips vs micro chips on the edge as a result. Now which of these means better edge retention? IDK,
 
Metamorph said:
Is wear resistance and edge retention the same thing? Also what is the reason for toughness and wear resistance being directly opposing properties? Not challenging what you said, just want to learn more.
Click to expand...
From my personal perspective and understanding, not the most accurate, but I believe that it is correct and easy to understand:

Wear resistance is probably the most important contributing factor to edge retention, but not the same. Wear resistance is about the material property, how much it wears off vs other material. Edge retention is about application property, how long the edge will hold while cutting.

Wear resistance is generally about hardness. Most metals by themselves, including iron, are quite soft. The hardness comes from the amount of cementite and crystal structure formed using carbon (carbide) or other elements. Nevertheless, the harder they get, the more brittle they become. Cast iron is extremely high carbon (by steel standard) iron alloy, it is hard, but can't be used to make blade as the edge will break into small dust easily, due to the tiny chipping.

The "toughness" is to keep the blade from chipping, specifically from micro chipping, and therefore it will preserve the edge sharpness, increasing the edge retention.

Though, with the advancement in technology, such as powder metallurgy, over 1.8% Carbon alloy, the carbon level of cast iron alloy, are now granted higher strength/toughness and could be used for blades.

Cross section of the edge, angle of grind, etc, come in to play with edge retention as well.

Larrin is a professional, he used the correct wording.
 
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