Rockwell hardness in relation to compressive strength

[Hunter21]

Something I am trying to better understand is how much rockwell hardness directly relates to compressive strength. Toughness aside, I have always understood that the higher the RC value then the stronger the knife edge was, harder to dent and ding it. But the more I read and try to educate myself, there seems to be exceptions to the rule and I just want to learn why. In example, if one were to make a blade out of S5 steel at 60RC, it seems on paper that it should be extremely tough and strong. But I see many people comment that even at this hardness, it will dent/deform more than some other steels at the same hardness, say 3V (correct me if I'm wrong). Anyone have a dumbed down explanation?

 

[chiral.grolim]

Something I am trying to better understand is how much rockwell hardness directly relates to compressive strength. Toughness aside, I have always understood that the higher the RC value then the stronger the knife edge was, harder to dent and ding it. But the more I read and try to educate myself, there seems to be exceptions to the rule and I just want to learn why. In example, if one were to make a blade out of S5 steel at 60RC, it seems on paper that it should be extremely tough and strong. But I see many people comment that even at this hardness, it will dent/deform more than some other steels at the same hardness, say 3V (correct me if I'm wrong). Anyone have a dumbed down explanation?

Yes, Rockwell hardness is determined by an alternative method to Brinell hardness but relates in a direct, linear way to compressive and yield strength, a non-destructive means of testing by indenting (compressing) the piece over a small area. Typical knife-blades are hardened to >55Rc to resist deformation of the thin cutting edge. When the strength is exceed, a "brittle" steel will suffer very little plastic deformation prior to fracture while a "ductile" steel will suffer more plastic deformation prior to fracture.

As to use of S5, availability has been very low vs. S7 shock-steel. S7 is used by a few makers/producers, Scrapyard and Survive! among them, but most opt for L6, 5160, 1095, 52100, INFI, etc. I assume that much of this has to do with the cost of stock and heat-treatment to get the desired attributes (?). One of those attributes is wear-resistance conferred by carbide-content (carbon + formers). While S5 and S7 indeed have very high toughness at 58-60 Rc (>150J), that toughness plummets at 60-61Rc (only ~66J, similar or lower than CPM-3V). Keep in mind that such high toughness may not be detectable in the fine edge of a knife-blade or not experiencing the kinds of impacts for which S5 and S7 were designed. Furthermore, the composition produces no carbides to prevent abrasive/adhesive wear while 3V can outperform D2 and present considerably more corrosion resistance than S5. So in the end, it's a matter of achieving the necessary balance of fracture-resistance, wear-resistance, and corrosion-resistance. In rope-cutting tests, users have noted that higher-carbide steels maintain a sharp cutting-edge longer than low-carbide steels at the same hardness and geometry.

http://www.crucibleservice.com/eselector/prodbyapp/tooldie/t&dchemtbl.html

 

[Charr]

Yes, Rockwell hardness is determined by an alternative method to Brinell hardness but relates in a direct, linear way to compressive and yield strength, a non-destructive means of testing by indenting (compressing) the piece over a small area. Typical knife-blades are hardened to >55Rc to resist deformation of the thin cutting edge. When the strength is exceed, a "brittle" steel will suffer very little plastic deformation prior to fracture while a "ductile" steel will suffer more plastic deformation prior to fracture.

As to use of S5, availability has been very low vs. S7 shock-steel. S7 is used by a few makers/producers, Scrapyard and Survive! among them, but most opt for L6, 5160, 1095, 52100, INFI, etc. I assume that much of this has to do with the cost of stock and heat-treatment to get the desired attributes (?). One of those attributes is wear-resistance conferred by carbide-content (carbon + formers). While S5 and S7 indeed have very high toughness at 58-60 Rc (>150J), that toughness plummets at 60-61Rc (only ~66J, similar or lower than CPM-3V). Keep in mind that such high toughness may not be detectable in the fine edge of a knife-blade or not experiencing the kinds of impacts for which S5 and S7 were designed. Furthermore, the composition produces no carbides to prevent abrasive/adhesive wear while 3V can outperform D2 and present considerably more corrosion resistance than S5. So in the end, it's a matter of achieving the necessary balance of fracture-resistance, wear-resistance, and corrosion-resistance. In rope-cutting tests, users have noted that higher-carbide steels maintain a sharp cutting-edge longer than low-carbide steels at the same hardness and geometry.

http://www.crucibleservice.com/eselector/prodbyapp/tooldie/t&dchemtbl.html

I love this explanation. Probably one of the most informative posts I've seen in a very long time!

I can second this information, and will say that my personal experience will back up this data. However, there are some people who are able to HT S7 to perform better at higher hardnesses, though not many people. In my experience, Eliot at Ferrum Forge does S7 the best for my uses, though he does it in generally thick stocks for swords and heavier cutting tools.

Though Rockwell will normally be able to tell you most of the properties of a steel based on the recommended heat treatment formulas, there are definitely some exceptions. There are some treatments that can leave steels at the same hardnesses and have different overall propeties, though admitadly these differences are often relatively small for users. there are steels that have some very odd characteristics at different hardnesses though.

I think the answer above is pretty much perfect as a general rule, but I'm just saying there can be some variation depending on the specific heat treat.

 

[Charr]

Also steels usually have a functional range of hardness in which they will perform best. M390 is usually agreed to be 59-61, S35VN is 58-61, 3V is 57-63 (the extremes have differing characteristics), etc.

Within those ranges you will see the steel perform mostly the same, with gradual changes in the properties as the hardness increases/decreases. There are some steels though that operate farther apart. I've seen 4V and M4 varry anywhere from 57-65, and I've even seen M4 at 67rc. The properties of the steel obviously change greatly in that large of a range, and some people will not like the way the steel performs for many tasks depending on where the hardness falls (again, keeping in mind hardness is only a relative indicator of the overall heat treat).
Depending on how they're treated, many steels will jump above and bellow one-another in many categories, from toughness to wear resistance, and you will see some steels eventually become unusable for knives, while others will excell greatly at the same hardness.

Its a hug balancing act trying to get all of it figured out and finding the right steel for you. The different properties of different steels are not simple to understand over the range of heat treats that can be done on the steels.

 

[bodog]

I'm not an expert, far from it, but i know you can take two bars of the same steel and wind up with equal hardness but one is considerably weaker because someone overheated the blade or blew the temper. I know that's a generic answer, but the quality of heat treatment is more important than final hardness of any steel. I'd rather get an optimally heat treated at a lower or higher hardness than I want than a sub-optimally heat treated knife right at the specifc hardness I want.

It gets into stuff I'm not very knowledgeable about like grain growth, crystalline structures within the steel, which way the grain runs through the blade, pearlite, bainite, cementite, etc. Hopefully one of these other guys can get into why Rockwell hardness matters less than ensuring a knife is finished with the optimal grain and crystalline structures.

I wish it was as easy as saying "I want 3V at 61 RC." Instead we should be saying we want 3V that maximizes toughness and edge retention without worrying about corrosion resistance. Even that's really too simple of a blade description.

Long story short, Rockwell hardness points tell one small part of the story. An S7 blade at 58 HRC may perform well and be tough as hell and can take a beating with a sledgehammer while another S7 blade at 58 HRC may crumble the first time you drop it. Hell, look at the 3V Nathan puts out. Now, 3V is tough and everyone know it, but he takes the same steel, treats it right, and then pounds on it with, literally, a sledgehammer through solid concrete with only very minor rolling and definitely no catastrophic failures or even the edge bevel being that torn up. His blades aren't even that thick and the edge bevel angles are not unrealistic for a fixed blade knife meant for abusive work. They're actually pretty acute for that kind of knife.

 

[Ankerson]

I'm not an expert, far from it, but i know you can take two bars of the same steel and wind up with equal hardness but one is considerably weaker because someone overheated the blade or blew the temper. I know that's a generic answer, but the quality of heat treatment is more important than final hardness of any steel. I'd rather get an optimally heat treated at a lower or higher hardness than I want than a sub-optimally heat treated knife right at the specifc hardness I want.

It gets into stuff I'm not very knowledgeable about like grain growth, crystalline structures within the steel, which way the grain runs through the blade, pearlite, bainite, cementite, etc. Hopefully one of these other guys can get into why Rockwell hardness matters less than ensuring a knife is finished with the optimal grain and crystalline structures.

I wish it was as easy as saying "I want 3V at 61 RC." Instead we should be saying we want 3V that maximizes toughness and edge retention without worrying about corrosion resistance. Even that's really too simple of a blade description.

Long story short, Rockwell hardness points tell one small part of the story. An S7 blade at 58 HRC may perform well and be tough as hell and can take a beating with a sledgehammer while another S7 blade at 58 HRC may crumble the first time you drop it. Hell, look at the 3V Nathan puts out. Now, 3V is tough and everyone know it, but he takes the same steel, treats it right, and then pounds on it with, literally, a sledgehammer through solid concrete with only very minor rolling and definitely no catastrophic failures or even the edge bevel being that torn up. His blades aren't even that thick and the edge bevel angles are not unrealistic for a fixed blade knife meant for abusive work. They're actually pretty acute for that kind of knife.

It's really best to find a good knowledgeable knifemaker that knows what they are doing 1st.

Then let them know what the said knife will be used for, I mean exactly and 100% truthful.

I am sure they could make a knife to suit your needs and would perform to the expected level spoken about before hand.

1. Use is the most important part and 1st before anything else.

2. Next would be design/geometry what design would work best for the intended use.

3. Then and only then what steel is going to work best for the use and design.

4. After that the maker makes the knife and tests it to make sure it performs to the expectations before it goes off to the customer.

 

[bodog]

It's really best to find a good knowledgeable knifemaker that knows what they are doing 1st.

Then let them know what the said knife will be used for, I mean exactly and 100% truthful.

I am sure they could make a knife to suit your needs and would perform to the expected level spoken about before hand.

1. Use is the most important part and 1st before anything else.

2. Next would be design/geometry what design would work best for the intended use.

3. Then and only then what steel is going to work best for the use and design.

4. After that the maker makes the knife and tests it to make sure it performs to the expectations before it goes off to the customer.

Truth, but the hard part, unless you're at least fairly knowledgeable yourself, is separating the wheat from the chaff. It's hard to find a quality maker unless they come out and either show testing videos of their blades or take an active interest in participating in these types of forums and explain what they do and why. Even with the little I know I find it hard to contact a maker and try to discuss anything without sounding like a complete moron to myself. There's a lot to it, more than just Rockwell hardness. I'm still curious about blunt cut and his superquenching methods and the results of those methods.

 

[Ankerson]

Truth, but the hard part, unless you're at least fairly knowledgeable yourself, is separating the wheat from the chaff. It's hard to find a quality maker unless they come out and either show testing videos of their blades or take an active interest in participating in these types of forums and explain what they do and why. Even with the little I know I find it hard to contact a maker and try to discuss anything without sounding like a complete moron to myself. There's a lot to it, more than just Rockwell hardness. I'm still curious about blunt cut and his superquenching methods and the results of those methods.

Don't get me started on that marketing thing, it's marketing BS and I will just leave it there, think buzzword.....

They don't have access to the right equipment to even begin to accomplish what they think they are, I don't care how many times they say they temper it, it isn't going to happen.... NEVER.

An actual Scientist that actually works in that field they trying to talk about posted some reality over on the Spyderco forum, but that all seemed to get ignored in favor of the typical BS.

He and some others I spoke with thought it was very amusing if you get my point.

Now if they dug up a few Million Dollars in the past few weeks and had Aerospace level Furnaces installed in their shop or house then maybe.

Other than that..... No freaking way.

There are some good makers here on BF, good respectable makers with excellent reputations.

The best thing to do is like I posted start with what you will use the knife for and move on from there, a good knife maker can walk you through the process.

There are no dumb questions when speaking to a knife maker that will be making you a knife.

 

[RevDevil]

Off to Shoptalk...

 

[chiral.grolim]

Hell, look at the 3V Nathan puts out. Now, 3V is tough and everyone know it, but he takes the same steel, treats it right, and then pounds on it with, literally, a sledgehammer through solid concrete with only very minor rolling and definitely no catastrophic failures or even the edge bevel being that torn up. His blades aren't even that thick and the edge bevel angles are not unrealistic for a fixed blade knife meant for abusive work. They're actually pretty acute for that kind of knife.

Aren't his knives designed as "fighters"? From a video i saw of him hammering one into a cinder-block, he stated that the blades are sharpened to 20-dps and >0.030" behind the edge, quite stout as expected for a knife designed to be abused, not much different than a blade from ESEE or Becker/Kabar or Buck or Gerber, similar to what Survive! uses on the GSO-4.1 in 3V and even M390 with similar results (and lower toughness on paper):

https://www.youtube.com/watch?v=gFzI9U64bjg

Remember Noss from Knifetests.com? Some of his D-test videos have been re-uploaded featuring chopping concrete and what was lovingly called "the hammer of truth" https://www.youtube.com/channel/UCReKyb0rO1E2Leamipn7Yfg/videos?sort=da&view=0&flow=grid

A cheap chinese-mystery-steel blade being smashed into concrete: https://www.youtube.com/watch?v=_yt1l68PS1M

What I am getting at is, while you are absolutely right that HT makes all the difference in terms of the microstructure of the steel that can vary considerably at the same hardness depending on the protocol, ways of testing superiority of one steel/HT/company vs another may not be as easy as such dramatic tests may indicate. If a 420HC Buck can handle abuse as well as a CPM-3V blade from another maker, it could indicate that Buck is the better maker since they achieved the same result with a 'lesser' steel... or it could indicate that the geometry of each is too thick to demonstrate superiority of one over the other in such a test. No disrespect for Nathan's work, I just don't regard that performance as impressive. *shrug*

 

[bodog]

Don't get me started on that marketing thing, it's marketing BS and I will just leave it there, think buzzword.....

They don't have access to the right equipment to even begin to accomplish what they think they are, I don't care how many times they say they temper it, it isn't going to happen.... NEVER.

Quite possibly, but there hasn't been any objective testing to confirm or dispel it. Until then, I have no reason to call him a liar or anything, I'll just sit on the sidelines waiting to hear from the dudes he just gave blades to a couple of weeks ago. Hopefully they post some good reviews. And I agree with the other stuff you said.

 

[Ankerson]

Quite possibly, but there hasn't been any objective testing to confirm or dispel it. Until then, I have no reason to call him a liar or anything, I'll just sit on the sidelines waiting to hear from the dudes he just gave blades to a couple of weeks ago. Hopefully they post some good reviews. And I agree with the other stuff you said.

Well unless they won the lottery in the last week to two it's not ever going to happen.

The equipment they would need to even begin costs Millions.

The quench rates will never be fast enough with conventional equipment to even get started.

That's reality.

 

[bodog]

Aren't his knives designed as "fighters"? From a video i saw of him hammering one into a cinder-block, he stated that the blades are sharpened to 20-dps and >0.030" behind the edge, quite stout as expected for a knife designed to be abused, not much different than a blade from ESEE or Becker/Kabar or Buck or Gerber, similar to what Survive! uses on the GSO-4.1 in 3V and even M390 with similar results (and lower toughness on paper):

https://www.youtube.com/watch?v=gFzI9U64bjg

Remember Noss from Knifetests.com? Some of his D-test videos have been re-uploaded featuring chopping concrete and what was lovingly called "the hammer of truth" https://www.youtube.com/channel/UCReKyb0rO1E2Leamipn7Yfg/videos?sort=da&view=0&flow=grid

A cheap chinese-mystery-steel blade being smashed into concrete: https://www.youtube.com/watch?v=_yt1l68PS1M

What I am getting at is, while you are absolutely right that HT makes all the difference in terms of the microstructure of the steel that can vary considerably at the same hardness depending on the protocol, ways of testing superiority of one steel/HT/company vs another may not be as easy as such dramatic tests may indicate. If a 420HC Buck can handle abuse as well as a CPM-3V blade from another maker, it could indicate that Buck is the better maker since they achieved the same result with a 'lesser' steel... or it could indicate that the geometry of each is too thick to demonstrate superiority of one over the other in such a test. No disrespect for Nathan's work, I just don't regard that performance as impressive. *shrug*

You have to admit that those videos Nathan shows directly relate to a Rockwell hardness in relation to a compressive strength discussion. There's a hell of a lot of compression happening to the edges and spines of his blades in those videos, that's what the OP was asking about. And for sure, if that knife is meant as a "hard use" knife, then the guy should send one to Noss to test if he feels it can withstand it. Personally, I think it actually might.

 

[chiral.grolim]

Don't get me started on that marketing thing ... buzzword.....

How much of INFI's performance is marketing BS? And their SR101 (52100 mod)? Both names are buzzwords and well done :thumbup: Buck used to market their blades by hammering them through steel bolts The Survive! video linked above and Nathan's videos - marketing. ESEE puts out their "no questions asked lifetime warranty" (that only applies to low-hardness 1095 blades). Lock-strength tests that go well beyond what the average user would inflict? Sometimes a good maker/producer just needs a good marketing tool/phrase to help get their product into the hands of customers. Like you wrote, lots of "good respectable makers" here that had to work to make their products stand-out from those around them, be it beautiful pictures or an aura of mystery or dramatic demonstrations of performance. Even if bluntcut's "super-quench" isn't what he thinks/claims, his product may still meet or exceed customer expectations, if only he can get them to buy And it beats appeals to "super secret ninja special forces unit"


But I'm de-railing the thread, my apologies.

 

[Ankerson]

How much of INFI's performance is marketing BS? And their SR101 (52100 mod)? Both names are buzzwords and well done :thumbup: Buck used to market their blades by hammering them through steel bolts The Survive! video linked above and Nathan's videos - marketing. ESEE puts out their "no questions asked lifetime warranty" (that only applies to low-hardness 1095 blades). Lock-strength tests that go well beyond what the average user would inflict? Sometimes a good maker/producer just needs a good marketing tool/phrase to help get their product into the hands of customers. Like you wrote, lots of "good respectable makers" here that had to work to make their products stand-out from those around them, be it beautiful pictures or an aura of mystery or dramatic demonstrations of performance. Even if bluntcut's "super-quench" isn't what he thinks/claims, his product may still meet or exceed customer expectations, if only he can get them to buy And it beats appeals to "super secret ninja special forces unit"


But I'm de-railing the thread, my apologies.

Never said what he is doing won't perform, I am sure he wouldn't put a knife out that was a complete POS as it would totally kill his reputation almost overnight.

Wouldn't want to see that happen to anyone.

I am sure he will work out the HT he needs for the said steel, but it won't be anything close what I was reading about, that's way beyond conventional means in all reality.

 

[chiral.grolim]

You have to admit that those videos Nathan shows directly relate to a Rockwell hardness in relation to a compressive strength discussion. There's a hell of a lot of compression happening to the edges and spines of his blades in those videos, that's what the OP was asking about. And for sure, if that knife is meant as a "hard use" knife, then the guy should send one to Noss to test if he feels it can withstand it. Personally, I think it actually might.

Noss is done, no more tests, which is too bad as it sure got Strider and CRK and BRKT fans in a tizzy

Yes, impact-shock and compression definitely happening in those vids :thumbup: What I ask is, if 420HC and M390 at similar geometry demonstrate similar resistance in such conditions, how is the enhanced durability of CPM-3V evident? Would it be evident if taken thinner, or would the stress exceed the threshold for all in similar fashion? If the latter than is this test anything more than a demonstration of durability on-par with Buck (and above that of Strider and CRK, based on Noss' work )? Another question back on topic: how would one test their S5 or S7 or even CPM-3V knife blade to demonstrate superior toughness over steels like M390 with higher wear or 420HC with less? It may turn out that such high toughness as demonstrated by Charpy isn't so important for knife use...

My guess is that one would see the enhanced durability after extended use, i.e. repeated beatings Jack-hammer bits and machining parts are built for longevity at proper geometry, hundreds of thousands of cycles, not something you're likely to see in the first few whacks. Fractures can take time to develop. You can't just fire a dozen rounds through a pistol and comment on its reliability. And with that in mind, what advantage is gained by using S5-steel in a knife-blade whose primary purpose is cutting as opposed to smashing concrete? Well, it might survive Noss

In contrast, what advantage would be gained from using a steel like S110V in a knife blade? It probably wouldn't survive Noss... but at an appropriate geometry it should keep cutting through normal stuff a LOT longer than the S5 blade.

 

[BluntCut MetalWorks]

Chiral - good posts :thumbup:

HRC is simply a number, sort of useful to indicate how much steel resist the indenter per given pressure(150kg). It won't tell you grain size or carbide type+size nor microstructure.

*** off topic - about my super quench (SQ)***
Considering

SQ cooling rate is too fast for steels with more than 0.6%C
Hence, Jim (Ankerson) - not sure what you are referring to multi-million dollars equipment? Aahh, is it Intensive Quench or other UHC high temp quench?

Is SQ a dumb or simple a marketing gimmick? Not to me, I stay within my area of tinkering/research interest - at whatever metallurgical experty or lack of. Could be educational/intriguing to ask, what happen when martensite transformation (Ms to Mf) taken place super fast. When steel expand super fast (martensite occupies more space than steel elements in other phrases), there need to room for such expansion. But there are grains with some average size and some various shapes. In order to keep this steel in one piece, over all misorientation angle across grain boundaries must be low. Otherwise with higher misorientation, jarring/fracturing will taken place, thus crack/break steel piece.

I am implying, in order to have a successful SQ, the steel needs fine aus-grain and other attributes intentionally aligned. Does the end products any better than std ht? I think so but can't quantify yet.

For those curious makers/metallurgists/tinkers want a challenge - well, give SQ a shot.
pick a steels: 52100/W2/1095/CruV - 1/8" thick coupon (2"x3" piece)
ht: normalize -> harden 1500F-1525F 10 minutes soak, SQ (60F-90F), temper 400F for 5 minutes.
Verify: Ferric Chloride etch -> surface grind. Success if no cracks.

 

[Nathan the Machinist]

My name got mentioned a couple times here so I thought I might chime in.

I don't mean to be associated with concrete hacking and other parlor tricks. There is a history here and I'd like to explain it.

First let me say that any thick piece of well tempered hardened steel can break up a cinder block without much trouble and the characteristics that make for a good concrete basher don't generally align well with a good cutting tool. I get that and I don't try to mislead people into thinking otherwise.

I am making some rough use knives for folks who want something specifically made to tolerate use that the majority of you folks would never need or want. This isn't rocket science and can easily be accomplished with any old lath martensite at a moderate hardness and thick geometry. All I did was try and find alloys particular well suited to this and try to optimize both the heat treat and the geometry so the finished work could be as thin and light as possible while still filling that need.

It's common knowledge that CPM 3V is a very durable steel. This is a function of the type of martensite formed, the relatively low volume of "stuff" that detracts from strength in thin sections such as retained austenite, large carbides, inclusions, and areas of excessive alloy such as the globs of free chromium (that strengthen a steel in thick sections) found in conventional chrome steels.

The work I did was to tweak the heat treat from one optimized for stamping tools to one for cutlery. 3V was intended to be a die steel that has the abrasion resistance of D2 and the toughness of A2. Really quite simple. They did this by avoiding plate martensite and achieving abrasion resistance with a lot of fine vanadium carbide. They addressed retained austenite with the secondary hardening hump. A nice clean, relatively soft matrix with lots of fine vanadium carbide "aggregate" makes a good stamping tool. However any steel, when applied to a thin knife edge, will have problems with carbon lean martensite and too much carbide. 3V actually does quite well compared to most, but it still benefits from a relatively rapid quench to Mf to prevent (or reduce) RA and eliminate the need for the secondary hardening hump. The thin sections and relatively uniform thickness of a knife blade and reduced concern for dimensional stability make cutlery fundamentally different than tool&die. The improvement in edge stability and edge retention are significant. The purpose of those videos was not to show how super-duper tough the knife was, it was to demonstrate that despite tweaks I'd made to improve edge retention and cutting performance it was still durable.

I don't want folks to think "oh, that Nate guy, he makes indestructible pry bars, bleh". On the contrary, I'm trying to make rough use knives that aren't so unnecessarily thick, heavy and obtuse so they can still cut and be carried. Anything can cut a cinder block if it's thick and soft enough. I'm trying to make something that will do that while having good edge retention and cutting performance.

 

[james terrio]

The short answer is... there's really no such thing as a short answer. Rockwell hardness is a useful measurement, but it's deeply inadequate as an overall yardstick of how strong or tough a knife blade is.

If one really wants to get into figuring out which alloys exhibit high strength and high toughness and high wear-resistance, one would be well-served to read Kevin Cashen's thoughts on basic steel structure (especially including lath vs. plate martensite), then peruse a dude named Roman Landes' papers, and then perhaps spend some time with a cat called Brad Stallsmith (and other folks who HT steel for a living), to learn a bit more about how various amounts of alloying elements affect HT protocols and might hurt/help a knife perform for specific tasks.

If there was such a thing as a short answer, in my opinion that answer would be that CPM-3V @ a minimum of 58Rc, as HT'ed by a pro-level shop with full LN cryo, offers the best balance of very high strength, very high toughness and excellent ability to take/keep a really fine edge, of all the currently-available cutlery steels. It also happens to have fairly good corrosion-resistance.

But even that "answer" isn't as simple as it seems... there are a few different ways to get to those hardnesses, with different properties...

 

[Hunter21]

Thanks everyone, this is very informative. I know there is no easy way to explain something that scientific in a couple paragraphs but this definitely helps.