CPM 154 characteristics

MatthewSB said:
Extremely interesting post, thank you ^

Maybe I'm misunderstanding the "on paper" definition of toughness. I based my earlier statement on a graph that showed CPM 154 having twice the "toughness" of CPM 20CV.

I still believe that CPM 154 will be perfect for people who don't need steel so tough that they can cut bolts in half (3V) at the expense of corrosion resistance, or so abrasion resistant that they can cut cardboard boxes for days on end (20CV) at the expense of sharpenability.
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Yeah, assessments of "toughness" can vary - some use the term to mean "tough to grind", some use it to mean "resistant to micro-chipping" but use very limited and subjective means of assessing this. I try to stick with charpy data with a good dose of metallurgical principles as observed through published academic controlled experiments. But that doesn't mean that what I'm presenting will fit with everyone's personal experiences.
*shrug* Not every knife made of one steel will show superiority in the expected aspects over a knife of another steel - HT and edge geometry play such huge roles in practical application... and when it comes to sharpening and use, specific user technique (and equipment) can again have such a major impact on perception of a given steel's attributes...
So if in your use of a given knife in a given steel, you find it superior to another knife in another steel, you know what you need to know regardless of the "on paper" properties of either... especially if it isn't clear how those "on paper" properties were established :p


Anyway, i completely agree with your final assessment - CPM-154 is good steel, may not be as tough as 3V or as wear-resistant as 20CV but may not need to be either, with a good balance of each and good corrosion resistance and ease of sharpening besides :thumbup: knife-knuts are so spoiled for choice :D
 
chiral.grolim said:
I would be VERY VERY surprised if this is true. The Charpy data I have seen on toughness shows that 154CM, 440C, S30V, S35VN, CPM-154, and 20CV are all in the 30-40 J range on longitudinal impact testing. They only differ on transverse toughness where applicability is questionable and the numbers are quite low, with the PM steels all rating about the same level above the ingots... differences are slight between the PM bunch.

Keep in mind that toughness tracks closely with carbide volume and carbide size/distribution. Wear resistance and ease of sharpening track closely with these as well, but carbide type then comes into play.

440C has 12% total carbide volume, all of it chromium-carbide and often includes pretty large aggregates.
154CM bumps this up to ~17.5% carbide, still all chromium, with a proportionate increase in aggregates. Toughness remains about the same despite this increase in carbide volume, the micron-scale is hard to assess with controlled testing. Keep in mind that these are "premium" ingot steels.

Using PM, CPM-154 maintains that same 17-18% carbide volume but presents increased toughness and wear at the micron scale due to the reduction in size and more homogenous distribution of the carbides (smaller aggregates).


Now take S30V or S35VN - these are 14.5% and 14.0% carbide steels, less than CPM-154 but with higher wear resistance and maybe a tiny bit more toughness that is not likely to be noticed. Why the jump in wear-resistance? Approximately 4% of that volume (~30% of the carbides in the steel) is MC-type vanadium carbide = smaller, harder/stronger/more wear-resistant than the chromium carbide in CPM-154. However, with that increased toughness and wear-resistance comes an edge less susceptible to grinding - it is harder to produce, more resistant to sharpening stones. Nevertheless, differences in sharpening on the micron-level using modern hones of appropriate grit of diamond or CBN will be un-noticeable, the abrasives are just so much harder than the steel matrix.

What about CPM-20CV? With it's increased carbon as well as carbide-formers, this steel should be 17-18% carbide just like CPM-154, but again utilizing MC-type vanadium carbides in place of some chromium carbide = more wear-resistance, more toughness (though probably not noticeable), and more difficulty grinding but about the same sharpening on diamond or CBN hones.


So again, if folk are finding CPM-154 tougher than CPM-20CV or even S30V, I would wonder at the phenomenon and what the differences are in HT protocol and final HRC since the latter steels should be both tougher and more wear-resistant than the former at a given hardness, though again the difference in toughness would be very hard to assess with such fine adjustments in carbide type/content. In comparison, CPM-3V at 60Rc presents ~100 J impact toughness, but it also is only ~5% carbide and mostly VC-type. A2 tool steel has similar carbide volume to 3V but presents ~53 J impact toughness at 60Rc and only ~half the wear-resistance. THAT is a difference.
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That's what I needed. Thank you!

Junkyard
 
Riz2530 said:
Correct. This my experience using both. I had a CPM bark river Bravo 1 that would get so rediculously sharp it was difficultto shave with. It would bite me. But... Remove bark from a 1 inch wide by 12 inch green stick and the edge was gone fast. It held an acceptible working edge though. But when I got 3V, i was shocked about how i could debark what felt like an entire tree and not lose the ability to shave. 20CV seems to be somwhere in between
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I've never debarked a tree with a knife. I have used a plain carbon steel axe for that task, and I could literally debark an entire tree with a roughly four inch sharpened face.
 
I guess I need to pull out my CPM154 Kershaws and see if I can get some experience, at least with edge holding. Can't check toughness much with a folder. That dang folding part is always the first to let go.
 
Silver Needle said:
I loved the bar graph, easy to look at and make comparisons. I just wish 20cv was on there.

The discussion between the metalurgists of our forum was good, but I had to think pretty hard to keep up with all the big words they learned while earning their hi skool daploma :p
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what kinda threw me with the graph was how s35vn seemed to be "the best" I wonder what they used to determine the ratings for each steel. One huge plus of getting into so called super steels, unless i start a rock cracking business, they will all likely outperform what i would need.
 
I'm not surprised about S35VN. Having used it in Zero Tolerance folders, it is right up there with ELMAX in my experience. And even better than an earlier ELMAX ZT. I think KAI changed their heat treat in their later ELMAX blades, because they certainly hold their edge better than one I have from about 2013.
 
Fancier, maybe I lost my sarcasm in the writing, it just seems as though 3V holds its edge for ever.
 
I cannot come close to matching the steel knowledge of most of the folks here. However, I have found cpm154 to be a lot more wear resistant than 3v. This is totally subjective and based onion easy it is for me toughest an edge on my 3v S!K vs how difficult it is to get the same edge on my cpm154 knife from Valkerie Knives. I prefer 3v, but like cpm154 just fine.
 
redwood22 said:
what kinda threw me with the graph was how s35vn seemed to be "the best" I wonder what they used to determine the ratings for each steel. ...
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Yeah, that chart is subjective "experience based measures", i.e. they surveyed some guys/gals and asked how they felt about the performance of various steels in terms of those 4 categories. I doubt those surveyed really made much effort to separate edge-retention into "chipping" vs "wear", otherwise there is NO WAY that S35VN would rate higher than CPM-3V in "chipping resistance", all other data (charpy, controlled comparisons, etc.) counters that. :p Not saying S35VN isn't reasonably tough, just that isn't its forte. *shrug*
 
The 4.7 is available in the presale now, so go get one and test CPM 154 for realz!
 
Probably a silly question but.... I know that the heat treat for 3V was recently refined, I'm assuming that CPM 154 is being heat treated by the same outfit, and the HT should be equally optimal? Anyone know the RC of the '154, as used by Survive!?

ni1s said:
The 4.7 is available in the presale now, so go get one and test CPM 154 for realz!
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Thanks for the headsup! Ordered one to test :D
 
Just what I needed... another blade (4.7). :rolleyes: Got it in 3V. Not really interested in 154.
 
SURVIVE! Ellie said:
The CPM-154 is around 59-60 Rc. All of the current steel/heat treat combos end up at 59-60 Rc.
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Thanks!

One more request - Reading posts in the Survive! forum, it seems like there are a lot of people who are new to CPM154 in general, and obviously new to it in a Survive! knife. Is there any feedback, or information from testing the steel in the field, that you could share? Specifically, how your CPM154 compares with your optimized 3V and 20CV?
 
Bark River uses is it a lot, or used to. They phased it out in favor of S35VN and 20CV.
 
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