Hardness vs. Toughness?

J

jerrywyatt77

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Feb 10, 2014
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Greetings, my name is Jerry, I am new to this forum and type of medium in general. I have a basic question for the seasoned knife users out there.

I have always been a huge fan of tanto blades for a few reasons, and for the most part will always gravitate towards them be they fixed blade or folding. However, I have recently become more concerned with the type of steel my blade is made of and it's functionality. So, I understand hardness is related to durability, resistance to corrosion, deformity, etc. I also know toughness is related to the blades impact and breaking. What I am looking for and not getting clear info on is a happy medium between the two. Typically I go for CRKT tactical knives with a 2cr13 58-62HRC, or a H&K with a 9cr13 58-60HRC. I even really like the hard durablity of Benchmade's knives with 154CM. But there are so many different types of tempered steel out there.

The actual question: Is there a steel out there that balances hardness and toughness (maybe a little more on the toughness side as I need a knife that can sustain repeated impact). and is a good all around knife?
 
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In production knives it seems that 1095 and S3V are good steels with good toughness. It might be an older steel but 440C is pretty good in that regards too.

You have to understand that hardness and toughness are sort of opposites. Any knife has to be a compromise between these 2. If you want good edge-holding then you have to compromise toughness towards hardness. If you want toughness then you might reduce the hardness a little bit. From one steel to another you change the point at which this tradeoff occurs. Also in general stainless steels will be less tough than carbon steels. But there are a lot of different steels out there and these are just crude generalizations.
 
Interesting topic that I would like to hear more on. Personally I think most modern knives are way to hard and biased towards the mythical edge holding ability. While I believe some of these high hardness knives do hold their edge longer they are equally more difficult to sharpen and MUCH more prone to breakage. I actually think the knife world is now missing the mark a bit with the focus on "hard use" knives capable of batoning and other such activities and at the same time trying for hardness levels that in fact make these knives much more fragile than they appear to be. I would prefer more of the Bo Randall approach. I often hear Randall Made Knives are too soft, but the reality is they are excellent cutters sharpen easily and are near impossible to break.
 
A Benchmade 810 Contego with a 4" reverse tanto blade of CPM-M4 (62-64HRC) gives you a fairly good balance of hardness, toughness and wear resistance. Since it's not stainless you just need to maintain it a little more rigorously.

Properties of steel:

  • Hardness — resistance to deforming & flattening
  • Toughness — resistance to breakage & chipping
  • Wear resistance — resistance to abrasion & erosion
 
Aren't some steels tougher at higher hardness levels than others?

For example, I've heard that ELMAX has the same toughness at 62 HRC as S30V at 57 HRC
 
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