I think that CPM 154 is a perfect "middle ground" between 20CV and 3V.
The "numbers" show, I believe, that '154 has twice the toughness of 20CV and half the wear resistance, making it less likely to fail and easier to sharpen. For outdoors chores, I doubt that the difference in edge retention will be very noticeable.
For those who want a knife that is tougher and easier to sharpen than 20cv, but more stain resistant than 3V, CPM 154 looks like the perfect solution. I can't wait to try a 4.7 in CPM 154.
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.
