Steel is like a good internet rumor; a lot of mystique, some truth, some slight of hand and a whole lot of (mis)conceptions. In terms of corrosion resistance, 420HC is superior to both S30V or 154CM. We have run a number of tests/trials in our Engineering and QA groups over the a number of years, and 420HC consistently provides the best corrosion resistance. It is also better than 440C in this area.
As far as edge holding, using Buck's heat treat and edging process, S30V is best, 154CM next and then 420HC; I specifically reference Buck's processes here because we have (CATRA) tested other's products (heat treated and edged by them) and have found knives with 154CM, ATS34, etc do not perform (edge retention) as well as our 420HC; don't under estimate the value of heat treat and proper edging/sharpening.
On toughness, in most cases, S30V will probably outperform 420HC and 154CM. To obtain maximum sharpness and edge holding out of the 420HC, we push the envelope on hardness for this type of material. That is not to say 420HC does not have some ductility, but maximum toughness for 420HC would be obtained in the Rc 55-58 range, but that plays heck with edge retention. The chemistry of S30V is such that when properly heat treated it give very good edge retention and good toughness.
Oh, heat treat can also have an impact on corrosion resistance; poor/improper heat treat can negatively impact the corrosion resistance of all of these steels.
ATS34 is Japanese 154CM; the chemistry is virtually identical. ATS34 is produced by Hitachi in Japan, and 154CM is produced by Crucible Metals in the US- BTW, Crucible was just purcahsed in bankruptcy by someone else, but they are continuing operations. A number of years ago, 154CM was difficult to get for companies such as Buck, we did not use enough of it to make it worth while for Crucible to produce for us. But at the time Hitachi was more than willing to supply the cutlery markets. this changed a few years ago, and the availabilty of 154CM was no longer a problem and for us at least, became slightly less expensive than ATS34. Thus the transition to 154CM.
So, if you want a "user" knife, can afford the upcharge, and want the best edge retention, S30V is your best option. If you want a "looker"/display knife, don't spend the extra money, just go with the 420HC. If you want a good general use knife and can't afford the premium steel the 420HC also makes a good choice. To ME, the 154CM is not a value choice either way; it is better at edge retention than 420HC, but if you're going to spend extra for that, spend a littel more and get the S30V- that is a personal opinion (I hope I haven't offended any fans of 154CM). I have carried 420HC knives for many years. I do now carry an S30V small Vantage with Paperstone handles, but that's sort of like the car lot manager getting to drive one of the Ferraris, it's one of the fringe benefits of being in that role.
Bill Keys
Director of Manufcturing and Engineering
Buck Knives, Inc